Patent Publication Number: US-2012023916-A1

Title: Diesel CGR process and structure

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Ser. Nos. 61/400,704 of Aug. 2, 2010 and 61/404,169 of Sep. 29, 2010 and 61/404,346 of Oct. 4, 2010. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to diesel engines and, more particularly, to processes and structures for improving the efficiency of the combustion cycle, reducing the harmful emissions of diesels and the electronic control of such processes. 
     BACKGROUND OF THE INVENTION 
     To improve emission at part load operation, exhaust gas recycling (EGR) is widely used in diesel engines. By definition, exhaust gas is the gas exhausted by the engine, upon exhaust valve opening, that is, during blow down. Prior to that event, and after the commencement of the compression ignition, the cylinder gas is still in its combustion and expansion phase. By half stroke of the expansion phase, over 90% of the combustibles are combusted, however. The pressure and temperature of the cylinder gas suddenly drops by 3-6 folds upon exhausting. Thus the combustion gas of a diesel engine has many times higher temperature and pressure than its exhaust gas. 
     EGR in diesels is done by two ways. Firstly, by residual gas entrapment resulted, when the cylinder is incompletely flushed by intake air. Secondly, by external redirection of some exhaust gas form the exhaust manifold into the intake manifold. The first may be assisted by turbocharger turbine back pressure and by intake gas throttling. The second, by supercharging assist. 
     By combustion dilution, EGR reduces NOx emission but increases the HC, CO and PM (hydrocarbon, carbon monoxide and particulate matter—mainly soot) emissions. However, it displaces fresh intake air and thereby reduces the oxygen available for combustion, thus it reduces engine power and torque. This way, EGR works against engine downsizing. To counterbalance that effect, the EGR is often cooled at further expense of engine performance. 
     Although skilled artisans have devoted considerable R&amp;D toward the improvement of EGR systems by electronic controls, none could overcome the negative consequences of the intake air displacement problem, the major drawback of the EGR in diesels. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to overcome the diesel EGR intake air displacement problem by substituting or compounding the engine by a CGR (combustion gas recycling) process. 
     In the cylinders of a multi cylinder diesel engine, improvements therein according to the principle of the invention includes a manifold, which is pressurized by combusting, gas depleted from one cylinder of a multi cylinder diesel engine and—concurrently or sequentially—decompressed by depleting that manifold combustion gas—which may be still rich in combustibles—into the entrapped air of another cylinder of the same engine, as well as means to command such process by a CGR structure. 
     Unlike EGR, CGR does not displace intake air and, due to UHC and PM (unburned hydrocarbon and particulate matter or soot) as well as heat recycling, boosts engine performance by automatic HCCI (homogenous charge compression ignition) assist effect. The CGR rate can be higher than the EGR rate, resulting in cleaner emission. The CGR can be all times on at any engine load and speed. 
     It is another object of this invention to provide for partial CGR assist effect and for an all times on CGR process, which recycles heat. 
     It is yet another object of the present invention to provide for the electronic control of CGR and with that adjust engine performance or emission quality on demand by the operator or by the physical or logistical conditions. 
     It is yet another objective of this invention to provide for CGR of a single cylinder diesel engine as well. 
     It is yet another objective of the present invention to provide structures—including valves, leg pipes, manifolds or pressure tanks and a control system—for the CGR process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring to the drawings: 
         FIG. 1  is a pneumatic circuit diagram of a preferred embodiment of the invention, illustrating a CGR process. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     The above problems and others are at least partially solved and the above objects and others realized in diesel engines, when their EGR is substituted or supplemented by CGR or, when CGR is added to two or four stroke diesels lacking EGR. 
     According to the principle of the invention, the introduction of CGR is mainly practical in multi cylinder engines, using a small volume combustion gas manifold. However, it is also executable in single cylinder diesels with large manifold volume. 
       FIG. 1  illustrates a preferred embodiment of the invention by assembly  100 , comprising structures and processes, which will be specified in their functional order as follows: 
     Air—which may contain some other gases—is sucked in into open ended intake manifold  1 , and passes to air filter  2  for particulate matters and dust cleaning. Then it passes through cooler  3 , which is equipped with coolant feed line  31  and return-line  32  of water or other suitable liquid or gas of sufficiently low temperature. The cooled air temperature is monitored by temperature sensor C 3 , which feeds signal to the engine&#39;s computer, which maintains the process control necessary for the proper operation of the engine and its supplemental CGR. The air then is sucked in by compressor  4 , which boosts its pressure and thereby increases its mass flow rate. Compressor  4  is driven (powered) by drive D 6  and speed controlled through controls receiving control signal C 4  from said computer. Then, through intake valve  51 , the chilled and compressed air, intermittently enters into upper cylinder (working) space  56  of diesel engine cylinder  5 . Valve  51  is controlled by cam signal or action  51 , which comes synchronized from engine crankshaft  58 . Crankshaft  58  is monitored by said computer, though encoders signal C 5 . It may receive speed control signal as well (not shown). Drive D 6  may come from turbine  6  or from crankshaft  58 . These two cases correspond to turbocharging and supercharging processes respectively.  FIG. 1 , illustrates the turbocharging case.
 
Space  56  is of a quasi harmonically variable volume space, supplemented by the volume of pressure vessel  10 , which is dead space formed by the lag pipe connecting cylinder  5  and CGR valve  11 . Into space  56 , fuel  53  is injected intermittently, commanded by said computer through signal C 53 . In space  56 , said fuel burns into combustion gas, which may contain some high temperature residual unburned fuel (a composite of hydrocarbons and carbon) and oxygen, under high pressure. Said combustion increases the pressure—by at least a magnitude—of space  56 , which drives (powers) the engine, turning its crankshaft  58 . In case valve  11  is a poppet valve, operating in the cylinder head, vessel  10  however is eliminated.
 
In forward flow, space  56  intermittently receives CGR gas from vessel  12  through valve  11  and vessel  10 . In reverse flow, vessel  12  intermittently receives gas from space  56  through valve  11  and vessel  10 . In pipe  13 , the CGR flows forward and reverse intermittently between cylinder  5  and one of the cylinders—otherwise identical to cylinder  5 —of the same engine, sharing a common crankshaft  58 .
 
The CGR flows into space  56  only when pressure in space  56  is rising and at a higher level than the pressure level of vessel  12 . The CGR flows out from space  56  only when pressure in space  56  is falling and at higher level than the pressure level of vessel  12 . Thus the volume of space  56  pneumatically does not “see” the volume of vessel  12 . The two actions, notably the CGR gas inflow and outflow to and from space  56 , can however be consecutive, without any time separation. In such a case of operation, during the opening time of valve  14 , first CGR gas flows into and then out of space  56  in such a way that the two actions are separated by the volumetric minimum of space  56 .
 
The CGR flow is further restricted by limitations imposed on the timing of valve  14 , which includes the set time of valve opening and closing, in the following way:
 
Valves  51  and  52  are closed during any CGR flow into or out of space  56 . CGR inflow into space  56  may be early in the phase of pressure rising of space  56 . That is called early inflow. CGR inflow out of space  56  may be early in the phase of pressure falling of space  56 . That is called early outflow. CGR inflow into space  56  may be late in the phase of pressure rising of space  56 . That is called late inflow. CGR inflow out of space  56  may be late in the phase of pressure falling of space  56 . That is called late outflow. Early inflow may be followed by early outflow. Late outflow may be followed by late inflow. Late inflow may be followed by early inflow. However, very late outflow cannot be followed by very late inflow, while very late inflow can be followed by very early outflow. The end of the inflow can be inseparable from the beginning of the outflow; however the end of outflow cannot be inseparable from the inflow.
 
These operational restrictions distinguish this diesel CGR process from internal EGR (exhaust gas recycling), surcharging by air or other gases and other diesel engine technology, which may alter the diesel gas cycle by any gas addition or removal into or out of the cylinder space.
 
Valve  11  interrupts a pipeline, which connects vessel  10  to pressure vessel  12 , which represents the volume of common rail (CR) pipe  13 , which interconnects cylinder  5  with the rest of the cylinders of a multi-cylinder engine, which comprises cylinder  5 . Pipe  13  however may be eliminated, in which case vessel  12  is to be retained. Said computer monitors the pressure of vessel  10  by signals pressure P 10  and temperature C 10 , as well as oxygen (alpha) sensory signal (not shown separate). Valve  11  is a normally closed two-way electro-pneumatic valve, piloted alternatively by pressures P 10  and P 12  or by pressure P 12  only or by external pressure (not labeled). The pilot lines are solenoid or piezo-electronic controlled by needle valves using control signal C 5 , directly from crankshaft  58  or processed by said computer. Valve  11  however can be cam operated poppet valve using signal-action C 5 , in which case vessel  10  and its monitoring (P 10  and C 10 ) is eliminated, or P 10  and C 10  becomes cylinder space  56  monitoring. Vessel  12  and pipe  13  may be configured to be a common structure, called CGR manifold or combustion gas manifold. The pipe, which connects vessel  10  to space  56 , may be configured as a single structure, called leg-pipe. Such structures however may be formed by cavities formed in the cylinder head of cylinder  5 .
 
Vessel  12  is protected from overpressure through check valve  15  by the normally closed pressure relief valve  16 , which vents overpressure through open end  17 . Valve  16  is shown a passive spring loaded valve, which however can also be controlled by said computer, electronically and also can be eliminated, if overpressure protection is ensured otherwise. Valve  16  however can be eliminated, since valve  14  may also act as pressure relief valve or simply because pressure protection of vessel  12  is ensured by vessel sizing of vessel  12  and by the timing and operation of valve  14 .
 
Some service pressure, less than overpressure, is released from vessel  12  into catalytic converter  7  via commanded pressure relief line R 17 , which is passed by valve  14 , which is piloted by pressure P 12  and controlled by signal C 12  coming from said computer, processed or direct. Such service process may be necessary for afterburning or heating up processes due in converter  7  or by pressure release purposes. Vessel  12  is also monitored by said computer via signals C 12  and gauge pressure P 12  or its corresponding pressure or temperature or oxygen contents, similarly to the monitoring of vessel  10 . Open end  17  may however be directed to converter  7  or muffler  8 .
 
The lower cylinder space  57 , the crank case) is vented trough open ended vent  59  and fed by oil line  54  and scavenged by oil line  55 . However, the crank case oiling may not be pumped externally, but by the piston moving in cylinder  5 . Crankshaft  58  gives control signals or actions C 51  and C 52  to command the intake and the exhaust processes of cylinder  5  respectively. Valves  51  and  52  are normally closed.
 
Space  56  is intermittently vented through exhaust valve  52 , which receives its control signal or action C 52  from crankshaft  58 . The gas leaving space  56  is called exhaust gas. Exhaust gas passes trough and powers turbine  6 , which has an output drive D 6 , which is connected to compressor  4 , powering it. Drive D 6 , however may be connected to a dynamo or other device to power other utility equipment.
 
Leaving turbine  6 , the exhaust gas pressurizes catalytic converter  7 , which may intermittently receive combustion gas from valve  14 , and which is pressure and temperature monitored through signal C 7 , which is fed into said computer. Converter may contain filters and afterburner units and choked by muffler  8 . Exhaust gas flows from converter  7  through muffler  8 , and from there exhausts through open tailpipe end  9 . Muffler  8  or the tailpipe gas may be temperature and alpha monitored by signal C 9 , which is also fed into said computer.
 
Filter  2 , cooler  3  and compressor  4 , as well as turbine  6 , converter  7  and muffler  8  may however be eliminated. Some of the gas flowing out of valve  52  may be returned to space  56  through valve  51 . Such process is called EGR (exhaust gas recycling), which does not interfere with the above specified CGR process. The opening time duration of valves  51  and  52  may overlap, but even that may not ensure the full scavenging of space  56 . In that case, some residual exhaust gas may remain in space  56  at the closing of valve  52 , which is called residual or inherent EGR. Some portion of the exhaust gas may also be diverted from after leaving turbine  6  to before entering compressor  4 . That process is called forced EGR, which reduces the amount of air, which space  56  may receive. Such reduction limits the oxygen available for combustion, and thereby the power, which can be harvested from crankshaft  58 .
 
     CGR can be two ways or one way only. In a two way CGR, the combustion gas flows in and out any or all cylinders, while in a one way CGR, it only flows out from one cylinder and flows into another. CGR fluctuates oscillating in the former and flows one way in the letter manifold or CG pipeline. Two-way flow CGR is twice as efficient as the one-way flow CGR. Finally, CGR works at all engine loads, not only at part load, as EGR does and unlike EGR, by heat recycling and retaining, CGR boosts engine efficiency and thereby saves fuel, while EGR does not. CGR allows passing excess air to the catalytic converter, improving its efficiency, even at very high engine loads. 
     The present invention is described above with reference to a preferred embodiment. However, those skilled in the art will recognize that changes and modifications may be made in the described embodiment without departing from the nature and scope of the present invention. For instance, chocking valves can be added to reduce gas flow in the CGR manifold and the CGR can be configured to be self-regulating without the use of computer control. Such configurations are hereby instructive. Also instructive the heat insulation or cooling said manifold or pressure vessels and their pipe connections. 
     Various further changes and modifications to the embodiment herein chosen for purposes of illustration will readily occur to those skilled in the art. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope thereof. 
     Having fully described the invention in such clear and concise terms as to enable those skilled in the art to understand and practice the same, the invention claimed is: