WO2012094369A2

WO2012094369A2 - Improved crankcase ventilation system

Info

Publication number: WO2012094369A2
Application number: PCT/US2012/020143
Authority: WO
Inventors: Steven D. Arnold
Original assignee: Arnold Steven D
Priority date: 2011-01-05
Filing date: 2012-01-04
Publication date: 2012-07-12
Also published as: WO2012094369A3

Abstract

A diesel oxidation catalyst (DOC) (10) is employed to oxidize oil contamination from gases received from the crankcase (8) through a ventilation line (12), thus eliminating any sticky, liquid hydrocarbons which typically adhere to turbocharger and charge air cooler surfaces. As the DOC requires a minimum temperature to light-off, die catalyst containment is designed for intimate contact with die exhaust manifold or turbine housing (16), which provides the temperature to activate the system.

Description

IMPROVED CRANKCASE VENTILATION SYSTEM REFERENCE TO RELATED APPLICATIONS

[Para 1 ] This application claims the priority of US Provisional Patent Application serial no. 614301 15 filed on 05 January 201 1 entitled IMPROVED CRANKCASE VENTILATION SYSTEM, the disclosure of which is incorporated herein by reference, BACKGROUND OF THE INVENTION

Field of the Invention

[Para 2] This invention relates generally to the field of emission control for internal combustion engines and more particularly to a crankcase ventilation system having a vent line routed from the crankcase and connected to a diesel oxidation catalyst (DOC) which receives blow-by gas through the crankcase vent line and has an outlet for the treated blow-by gas with the DOC is interconnected to receive heat from either a turbine housing or exhaust manifold.

Description of the Related Art

[Para 3] Emissions requirements for diesel engines ha ve necessitated the use of a closed crankcase ventilation system as crankcase gasses from engine blow-by would exceed emissions requirements on their own if ventilated to the atmosphere as commonly done in the past. In certain applications, these crankcase gasses are vented into the turbocliarger compressor inlet, where they contaminate the compressor impeller, diffuser and housing as w^rell as the charge air cooler. This contamination significantly reduces the performance of the turbocharger resulting in increased fuel consumption and/or increased emissions.

[Para 4] During the operation of a diesel engine there is some leakage of

combustion gas past the rings and into the crankcase. The valve seals and turbocharger seals can add to the leakage of combustion gas, commonly called "blow-by", into the crankcase. A build up of pressure in the crankcase is unacceptable as it reduces the power of the engine and may cause the oil seals to leak. Traditionally diesel engines have vented this gas overboard with a "draft tube". Some applications, such as ship marine engines, have used a coalescing filter to col lect as much of the oil as possible before venting it overboard. This keeps the engine room or bay much cleaner. However, with the stringent emissions now in place in most developed countries, this blow-by must be cleaned thoroughly.

[Para 5] Two methods have been in common use; closed crankcase ventilation and routing the blow-by into the engine after-treatment system. Closed crankcase ventilation routes the blow-by into the turbocharger compressor inlet, where it is consumed by the engine and its emissions system.

[Para 6] Unfortunately, the blow-by gas includes various hydrocarbons from oil vapor which can adhere to metal walls during its trip into the engine cylinder to be burned. These hydrocarbons have a particularly negative effect on the turbocharger compressor when diffusing in the vane-less diffuser. The flow friction increase is subs tantial and can reduce the compressor efficiency by 10% or more. A rule of thumb relating compressor efficiency and engine efficiency is that 4 points of compressor efficiency is worth one per cent fuel consumption.

[Para 7] In larger commercial diesel engines, the duty cycle of the engine may be high enough, combined with high pressure ratio of the compressor that the diffuser reaches a high enough temperature to oxidize the hydrocarbon buildup on the diffuser and restore the efficiency. In many engines, either the duty cycle is not high enough, or the power rating high enough (and thus the pressure ratio) to achieve sufficient temperature to oxidize the hydrocarbon buildup.

[Para 8] The state-of-the -art is to install a coalescing filter in the vent line, removing 90+% of the oil vapor, Still, even a few percent of oil vapor passing into the engine increases fuel consumption and emissions. There has been considerable development to increase the efficiency of coalescing filters and many are now in the mid- 90s. Commercial diesel engines typically run 500,000 miles or more between rebuilds, and even 5% inefficiency in a coalescing filter will result in hydrocarbon buildup on the compressor diffuser.

[Para 9] It is therefore desirable to provide a crankcase ventilation system which avoids contamination of turbocharger compressor diffusers. it is additionally desirable to reduce noise as a corollary effect of reducing the turbine wheel failures.

[Para 1 0] SUMMARY OF THE INVENTION [Para 1 1 ] The embodiments of the present application describe a diesel engine crarikcase ventilation system which employs an engine crankcase vent line routed from the crankcase and comiected to a diesel oxidation catalyst (DOC) which receives blow-by gas through the crankcase vent line and has an outlet for the treated blow-by gas. The DOC is interconnected to receive heat from either a turbine housing or exhaust manifold.

[Para 1 2] in certain embodiments, a check valve is employed in the crankcase vent line intermediate the crarikcase and the DOC. Additionally, a pressure regulator may be interconnected to the crankcase vent line for control of blow-by gas flow through the DOC. In exemplary embodiments the outlet of the DOC is connected to a mixer receiving charge air for input to a turbocharger compressor. Additionally, a heat exchanger comiected intermediate the DOC and mixer for cooling of the treated blow-by gas. In certain embodiments, the heat exchanger may employ compressor inlet air for cooling. BRIEF DESCRIPTION OF THE DRAWINGS

[Para 1 3] These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

[Para 1 4] FIG. 1 is a block diagram of a first embodiment employing a minimally configured system;

[Para 1 5] FIG. 2 is a block diagram of a second embodiment employing a ful ly configured system; and,

[Para 1 6] FIG. 3 is a block diagram of a third embodiment with overboard disposal of the vented gas,

DETAILED DESCRIPTION OF THE INVENTION

[Para 1 7] The embodiments described herein employ diesel oxidation catalysts (DOC), shown as element 10 in FIGs. I, 2 and 3 for oxidizing hydrocarbons in blow-by gas from a crankcase 8. For the example embodiments a platinum containing noble metal catalyst is employed in the DOC. Including a DOC in the closed crankcase ventilation (CCV) line 12 resolves contamination issues for turbocharger compressor and charge air oil cooler surfaces (for the embodiments of FIGs. 1 and 2). However, DOCs have a minimum temperature that they must reach before becoming active. This temperature is affected by the chemical composition of the catalyst and the concentration of

hydrocarbons (HC) being treated. Some conversion activity begins around 120C and full conversion efficiency is reached around 150C.

[Para 1 8] Blow-by gas, including soluble organic fraction (SO! ^'), from the crankcase will not reach this temperature, so an additional heat source must be used to bring the catalyst up to light-off temperature. The exhaust manifold and turbine housing are the hottest metal parts in the engine and are usually located near the crankcase vent line. For the embodiments shown, the exhaust manifold or turbine housing, generally designated 16 is redesigned to provide an adjacent passage for the DOC to receive heat, Q, from the hot exhaust manifold or turbine housing. The crankcase blow-by gas routed to the DOC which then provides a catalyzed exhaust gas (EG) to a mixer 18 combining charge air from air filter 20 with the crankcase gas for input into the inlet of compressor 22 in the embodiments of FIGs. 1 and 2 or to be dumped overboard or into the exhaust system (past any devices with a pressure drop), as represented by arrow 24 in FIG. 3.

[Para 1 9] The turbocharger compressor work is proportional to the inlet absolute temperature of the air (and gas) it compresses. The temperature increase of crankcase ventilation gas coming from the DOC is undesirable and will affect the pumping loop performance of the engine negatively. However, the volume flow of the crankcase ventilation gas is quite low compared to the fresh air flow of the engine, so this effect will be minimal.

[Para 20] The effect can be minimized by passing the flow through a heat exchanger 25 as shown for the embodiment in FIG. 2. An engine water heat exchanger will not be very effective as its temperature is not much lower than the crankcase gas. For exemplary embodiments, a gas-to-air heat exchanger is employed to dump the heat into the cooling air of the engine after it has passed through the major heat exchangers— charge air cooler, radiator, transmission cooler, air conditioning condenser, etc. The simplest method would be to use a finned tube to join the outlet of the DOC with the compressor air mixing junction.

[Para 21 ] Since the temperature out of the DOC will be high enough to burn oil , a check valve 26 is used before the DOC to unsure that a flow reversal does not cause an unintended oxidation of the oil in the crankcase. [Para 22] Coalescing filters are now standard on CCV systems and reduce the flow of hydrocarbons by 90+%, so leaving one in the system is advantageous as it reduces oil consumption as well as reduces the amount of heat going into the compressor inlet. For the embodiment of FIG. 2 a coalescing filter 28 is provided in the output of the crank case ventilation line. A coalescing filter is not required and could be eliminated on cost sensitive applications.

[Para 23] A pressure regulator 30 is typically used to make sure that the engine crankcase pressure is not allowed to operate beyond specified maximum and minimum pressures. In alternative embodiments, the regulator is designed into the coalescing filter or combined with the check val ve if a coalescing filter is not used.

[Para 24] To address the issue of HC-laden blow-by passing through the system before the DOC is up to temperature, it must be remembered that HC vapor or mist content will be low until the oil is hot, so an active DOC at start-up is not necessary. An electronically controlled pressure regulator is used in the embodiment shown to minimize the bypass of oil when the DOC is not active by raising the crankcase pressure to contain the blow-by in the crankcase temporarily until the DOC becomes active.

[Para 25] Depending on the emissions regulations (country specific), the treated blow-by could be dumped over-board as shown in the embodiment of FIG. 3; however the remaining emission constituents would be added to the main exhaust and have to meet the regulations.

[Para 26] Having now described the invention in detail as required by the patent statutes, those skilled in the art will recognize modifications and substitutions to the specific embodiments disclosed herein. Such modifications are within the scope and intent of the present invention as defined in the following claims.

Claims

WHAT IS CLAIMED IS:

1. A diesel engine crankcase ventilation system comprising:

an engine crankcase vent line (12) routed from a crankcase (8);

a diesel oxidation catalyst (DOC) (10) connected to and receiving blow-by gas through the crankcase vent line and having an outlet for treated blow-by gas, said DOC interconnected to receive hea t from one of a turbine housing or exhaust manifold (16).

2. The diesel engine crankcase ventilation system as defined in claim 1 further comprising a check valve (26) in the crankcase vent line intermediate the crankcase and the DOC.

3. The diesel engine crankcase ventilation system as defined in claim 1 further comprising a pressure regulator (30) interconnected to the crankcase vent line for control of blow-by gas flow through the DOC.

4. The diesel engine crankcase ventilation system as defined in claim 1 wherein the outlet of the DOC is connected to a mixer (18) receiving charge air for input to a turbocharger compressor (20),

5. The diesel engine crankcase ventilation system as defined in claim 4 further comprising a heat exchanger (25) connected intermediate the DOC and mixer.

6. The diesel engine crankcase ventilation system as defined in claim 5 wherein the heat exchanger employs compressor air for cooling.

7. A method for treatment of engine crankcase blow-by gas comprising:

connecting a diesel oxidation catalyst (DOC) to a crankcase vent line;

heating the DOC through intimate contact with one of an exhaust manifold or a turbine housing.

8 The method of claim 7 further comprising interconnecting a pressure regulator to the crankcase vent line for control of blow-by gas flow through the DOC.

9. The method of claim 7 further comprising inserting a check valve in the crankcase vent line intermediate the crankcase and the DOC.

10. The method of claim 7 further comprising connecting an outlet of the DOC to a mixer receiving charge air for input to a turbocharger compressor.

11 , The method of claim 10 further comprising connecting a heat exchanger mtermediate the DOC and mixer,

12. The method of claim 1 1 further comprising employing compressor air for in the heat exchanger.