Combustion Apparatus With Fuel Pre-Heating

Abstract

A combustion apparatus such as a Diesel engine ( 16 ) in a motor vehicle ( 1 ) has an air inlet system ( 20,22 ) through which air can be drawn air from the atmosphere to the engine, a fuel supply system ( 28, 30, 32 ) for supplying fuel to the engine, and an exhaust system ( 34, 36, 38, 40, 42 ) for exhausting combustion gas from the engine to the atmosphere. A heat exchanger ( 48 ) is provided between the exhaust system and the fuel supply system so that heat is transferred from the exhaust gas to the fuel so as to warm the fuel and thus improve the combustion efficiency of the engine. When applied to a conventional layout of motor vehicle the heat exchanger can conveniently be disposed beneath the vehicle away from the engine compartment so as not to cause overcrowding thereof. The heat exchanger may form part of an EGR system ( 44,46 ) for feeding a proportion of the exhaust gas from the exhaust system to the air inlet system so as to cool the recirculating exhaust gas and thus enhance the reduction of NO and NO 2 emissions.

1 . A combustion apparatus comprising a combustor ( 16 ) having an air inlet system ( 20 , 22 ) through which air can be drawn a from the atmosphere to the combustor, a fuel supply system ( 28 ,  30 ,  32 ) for supplying fuel to the combustor, and an exhaust system ( 34 ,  36 ,  38 ,  40 ,  42 ) for exhausting combustion gas from the combustor to the atmosphere, wherein a heat exchanger ( 48 ) is provided between the exhaust system and the fuel supply system so that, in use, heat is transferred from the exhaust gas to the fuel so as to cool the exhaust gas and warm the fuel. 
   
   
       2 . An apparatus as claimed in  claim 1 , wherein the exhaust system includes a loop portion ( 110 , 114 ) for feeding a proportion of the exhaust gas from a first point ( 112 ) in the exhaust system to a second point ( 116 ) in the exhaust system upstream of the first point relative to the main flow of exhaust has in the exhaust system, and the heat exchanger is provided between the loop portion and the fuel supply system so that, in use, heat is transferred from the exhaust gas in the loop portion to the fuel so as to warm the fuel. 
   
   
       3 . An apparatus as claimed in  claim 1 , wherein the exhaust system includes an exhaust gas recirculation system ( 44 , 46 ) for feeding a proportion of the exhaust gas to the air inlet system, and the heat exchanger is provided between the exhaust gas recirculation system and the fuel supply system so that, in use, heat is transferred from the recirculating exhaust gas to the fuel so as to cool the recirculating exhaust gas and warm the fuel. 
   
   
       4 . An apparatus as claimed in  claim 1 , wherein the exhaust system includes an exhaust return pipe ( 44 , 46 ;  110 , 114 ) and the fuel supply system includes a fuel feed pipe ( 28 , 30 ), a portion ( 58 ) of the fuel feed pipe being coiled around a portion ( 50 ) of the exhaust return pipe so as to form the heat exchanger. 
   
   
       5 . An apparatus as claimed in  claim 1  wherein the exhaust system includes an exhaust return pipe ( 44 , 46 ;  110 , 114 ) and the fuel supply system includes a sleeve ( 64 ) disposed around a portion ( 50 ) of the exhaust return pipe so that, in use, fuel passes between the sleeve and the portion of the exhaust return pipe and heat is exchanged. 
   
   
       6 . An apparatus as claimed in  claim 1 , wherein the exhaust system includes a catalytic converter ( 36 ) and is arranged such that the exhaust gas passes through the catalytic converter before passing through the heat exchanger. 
   
   
       7 . An apparatus as claimed in  claim 1 , wherein the exhaust system includes a silencer ( 40 ) and is arranged such that the exhaust gas passes through the silencer before passing through the heat exchanger. 
   
   
       8 . An apparatus as claimed in  claim 2 , wherein the wherein the exhaust system includes a silencer ( 40 ) disposed between said first and second points in the exhaust system and arranged such that the main flow of exhaust passes through the silencer. 
   
   
       9 . An apparatus as claimed in  claim 1 , wherein the heat exchanger employs a heat exchange fluid that, in use, flows between a portion ( 82 ) of the exhaust system and a portion ( 84 ) of the fuel supply system. 
   
   
       10 . An apparatus as claimed in  claim 9 , further including means ( 90 , 92 ) for controlling the flow of the heat exchange fluid in dependence upon the temperature of the fuel and/or the temperature of the exhaust gas. 
   
   
       11 . An apparatus as claimed in  claim 1 , further including a gas bypass ( 96 , 98 ) system for controlling the proportion of the exhaust gas that passes through the heat exchanger in dependence upon the temperature of the fuel and/or the temperature of the exhaust gas. 
   
   
       12 . (canceled) 
   
   
       13 . An apparatus as claimed in  claim 1 , further including means ( 118 ) for conditioning liquid fuel in the fuel supply system between the heat exchanger and the combustor. 
   
   
       14 . (canceled) 
   
   
       15 . A combustion apparatus as claimed in  claim 13 , wherein the conditioning means is operable to condition the fuel ultrasonically, using microwave energy, by other electromagnetic radiation and/or by electromagnets. 
   
   
       16 . A combustion apparatus as claimed in  claim 15 , further including means for varying the ultrasonic, microwave, electromagnetic radiation and/or magnetic field that is applied to the liquid fuel. 
   
   
       17 . (canceled) 
   
   
       18 . A combustion apparatus as claimed in  claim 1 , wherein the combustor comprises a diesel engine ( 16 ). 
   
   
       19 . A combustion apparatus as claimed in  claim 1  fitted to a motor vehicle ( 10 ), the motor vehicle having a fuel tank ( 24 ) disposed towards the rear ( 26 ) of the vehicle and an engine compartment ( 14 ) disposed towards the front ( 12 ) of the vehicle, the combustor being disposed in the engine compartment, the exhaust system ( 34 ,  36 ,  38 ,  40 ,  42 ) leading from the engine towards the rear of the vehicle, and the heat exchanger ( 48 ) being disposed beneath the vehicle away from the engine compartment. 
   
   
       20 - 22 . (canceled) 
   
   
       23 . A combustion apparatus as claimed in  claim 1 , wherein the heat exchanger is remote from the combustor. 
   
   
       24 . A combustion apparatus as claimed in  claim 1 , wherein the heat exchanger is arranged to transfer heat from the exhaust system to the fuel supply system independently of any cooling system of the combustor. 
   
   
       25 . An engine system comprising:
 an engine ( 16 ) having an air inlet system ( 20 , 22 ) through which air can be drawn from the atmosphere into the engine;   a fuel supply system ( 28 ,  30 ,  32 ) for supplying fuel to the engine; and   an exhaust system ( 34 ,  36 ,  38 ,  40 ,  42 ) for exhausting combustion gas from the engine to the atmosphere,   
     wherein:
 the exhaust system includes an exhaust gas recirculation system ( 44 , 46 ) for feeding a proportion of the exhaust gas to the air inlet system; and 
 a heat exchanger ( 48 ) is provided between the exhaust gas recirculation system and the fuel supply system so that, in use, heat is transferred from the recirculating exhaust gas to the fuel so as to cool the recirculating exhaust gas and warm the fuel. 
 
   
   
       26 . A motor vehicle ( 10 ) having:
 an engine compartment ( 14 ) disposed towards the front ( 12 ) of the vehicle;   an engine ( 16 ) disposed in the engine compartment;   a fuel tank ( 24 ) disposed towards the rear ( 26 ) of the vehicle;   a fuel supply system ( 28 ,  30 ,  32 ) for supplying fuel from the fuel tank to the engine;   an air inlet system ( 20 , 22 ) through which air can be drawn from the atmosphere into the engine; and   an exhaust system ( 34 ,  36 ,  38 ,  40 ,  42 ) for exhausting combustion gas from the engine to the atmosphere,   
     wherein:
 the exhaust system includes an exhaust gas recirculation system ( 44 , 46 ) for feeding a proportion of the exhaust gas to the air inlet system; 
 a heat exchanger ( 48 ) is provided between the exhaust gas recirculation system and the fuel supply system so that, in use, heat is transferred from the recirculating exhaust gas to the fuel so as to cool the recirculating exhaust gas and warm the fuel; and 
 the heat exchanger ( 48 ) is disposed beneath the vehicle away from the engine compartment.