Process for cooling diesel engine exhaust gases

• US 5,607,010 A
• Filed: 04/18/1995
• Issued: 03/04/1997
• Est. Priority Date: 04/26/1994
• Status: Expired due to Fees

• Current Assignee: MTU Motoren- und Turbinen-Union Friedrichshafen GmbH
• Original Assignee: MTU Motoren- und Turbinen-Union Friedrichshafen GmbH
• Inventors: Schmidt, Ralph-Michael, Schonfeld, Dieter
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): Sgantzos, Mark
• Application Number:
  US08/423,986
• Time in Patent Office: 686 Days
• Field of Search: 165/51, 165/52, 165/133, 165/905, 60/605.2
• US Class Current: 165/51
• CPC Class Codes: F02B 3/06 with compression ignition compression ignition engines using air or gas for blowing fuel into compressed air in cylinder F02B13/02
• CPC Class Codes: F02B 47/08 the substances including exhaust gas
• CPC Class Codes: F02M 26/06 Low pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust downstream of the turbocharger turbine and reintroduced into the intake system upstream of the compressor
• CPC Class Codes: F02M 26/24 with two or more coolers
• CPC Class Codes: F02M 26/28 with liquid-cooled heat exchangers
• CPC Class Codes: F02M 26/37 with temporary storage of recirculated exhaust gas internal exhaust gas recirculation F02M26/01
• CPC Class Codes: F05C 2225/04 PTFE [PolyTetraFluorEthylene]
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y10S 165/905 Materials of manufacture

Abstract

A process and a suitable arrangement for cooling diesel engine exhaust gases in an exhaust gas recirculation system is provided. In order to be able to avoid a contamination of the heat exchanger as well as a resulting required regenerating of the latter in the case of a cooling of the hot exhaust gas flow over a large temperature range, the cooling of the hot exhaust gas flow is carried out in at least two steps in that the exhaust gas flow flows successively through two heat exchangers which are each adapted to the corresponding cooling temperature range. By adapting the heat exchangers to specific small temperature ranges, even hot exhaust gas flows of up to 800° C. can be cooled to a desired low temperature by the series connection of a corresponding number of different heat exchangers, without causing significant contaminations of the exhaust gas cooling arrangement by exhaust gas particles. By the use of known heat exchangers, the construction of the exhaust gas cooling system becomes particularly reasonable with respect to cost.

Claims

1. Process for cooling diesel-engine exhaust gases in an exhaust gas recirculation system, a hot exhaust gas flow coming from engine cylinders first being cooled before being admixed on an intake side of an engine to an incoming fresh air flow,

wherein cooling of the hot exhaust gas flow is carried out in at least two successive steps, the hot exhaust gas flow being cooled in each cooling step to a different predetermined temperature, and

wherein the exhaust gas flow is cooled to a temperature of at least below 250°

C. before being subjected to a last of said at least two successive cooling steps.

2. Arrangement for cooling diesel engine exhaust gases in an exhaust gas recirculation pipe, comprising:

at least two heat exchangers connected in series with respect to an exhaust gas flow through said exhaust gas recirculation pipe, each heat exchanger being adapted to a different predetermined application temperature range; and

wherein at least a last of said at least two heat exchangers being adapted to an application in a temperature range below 250°

C. with respect to at least one of materials and coatings on parts of the heat exchanger contacted by said exhaust gas flow.

3. Arrangement according to claim 2, wherein exhaust-gas carrying parts of at least one heat exchanger are formed of high-temperature-stable, corrosion-resistant materials.

4. Arrangement according to claim 3, wherein exhaust-gas-carrying pipes of the heat exchangers are formed of titanium.

5. Arrangement according to claim 2, wherein at least one heat exchanger is provided which has plastic-coated, exhaust-gas carrying parts.

6. Arrangement according to claim 5, wherein the exhaust-gas-carrying parts are coated with polytetrafluoroethylene (PTFE).

7. Arrangement according to claim 5, wherein exhaust-gas-carrying pipes are made of polytetrafluoroethylene (PTFE).