GB2344854A

GB2344854A - Motor vehicle exhaust system

Info

Publication number: GB2344854A
Application number: GB9827791A
Authority: GB
Inventors: Thomas Tsoi Hei Ma; Jonathan Austin Ma
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 1998-12-18
Filing date: 1998-12-18
Publication date: 2000-06-21
Also published as: GB9827791D0

Abstract

The discharge section 20 of the exhaust system 10 is elongate, extends transversely of the vehicle and has a number of discharge regions (openings) 24 distributed over the length of the discharge section 20 so that the exhaust gases are diluted rapidly with ambient air. The invention positions the discharge section 20 to take advantage of the aerodynamics of the vehicle body. In figure 2, the floor pan 32 is streamlined, eg as a venturi, and the discharge section 20 is placed at the position of maximum air speed, eg at the throat of the venturi. Alternatively, the discharge section 20 may be located in a spoiler 33, figure 3, or angled downwardly in the rear bumper (34, fig.4).

Description

MOTOR VEHICLE EXHAUST SYSTEM Field of the invention The present invention relates to a motor vehicle having an engine exhaust system designed to minimise the concentration of noxious gases and particulate matter entering the cabin of a following vehicle.

Background of the invention Cabin air quality has attracted increasing attention with the realisation that the driver and passengers of a following vehicle could be exposed to higher concentrations of pollutants than pedestrians. This is because a second vehicle travelling behind a first vehicle will be directly exposed to the exhaust plume of the first vehicle. Although this exhaust plume is dispersed progressively with distance behind the first vehicle, a relatively high concentration of the pollutants could be drawn into the cabin of the second vehicle and breathed in by the occupants of the second vehicle. Micro-filters and absorbers for cleaning the cabin air are not particularly effective in that, while they remove some particulate matters and odours, the ultra-fine particles and noxious gases such as HC, CO and NOx will still get through.

By following a moving vehicle and measuring the dispersion of the exhaust gases at different distances behind the vehicle, it has been found that the air/exhaust dilution ratio reaches approximately 10: 1 at 1 metre, 100: 1 at 10 metres and 1000: 1 at 100 metres behind the vehicle.

Thus when two vehicles are travelling in tandem with a separation distance of 5 metres between the two, the occupants of the following vehicle could be exposed to the exhaust fumes of the first vehicle diluted to an air/exhaust dilution ratio of only 50: 1, assuming linear interpolation.

This concentration is significantly higher than that breathed in by a pedestrian walking by the side of the road where the exhaust gases would have dispersed to a dilution ratio of 500: 1 or higher.

The above problem has been addressed in the Applicant's earlier British Patent Application No. 9822484.3 which in one aspect is directed to a motor vehicle driven by an internal combustion engine having an exhaust system, wherein the discharge section of the exhaust system from which the engine exhaust gases are discharged into the ambient atmosphere is elongate, extends transversely to the direction of motion of the vehicle and comprises a plurality of discharge regions distributed over the length of the discharge section, the size and spacing of the discharge regions being such that the exhaust gases from the engine are thinly dispersed over a large distributed area, so as to be diluted sufficiently with ambient air within a short distance of leaving the discharge section of the exhaust system to increase above a predetermined minimum level the dilution of the pollutants in the exhaust gases at a predetermined distance behind the vehicle.

It is also known that the rate at which the exhaust gases are diluted after leaving the exhaust system affects the formation of nano-particles and rapid dilution assists in suppressing the formation of such particles.

The present invention relates to various modifications that can be made to a motor vehicle to assist in increasing the mixing of the exhaust gases with ambient air as quickly as possible after they have been discharged both to improve air quality in following vehicles and to suppress the formation of nano-particles.

According to a first aspect of the present invention, there is provided a motor vehicle driven by an internal combustion engine having an exhaust system, wherein the discharge section of the exhaust system from which the engine exhaust gases are discharged into the ambient atmosphere is elongate, extends transversely to the direction of motion of the vehicle and comprises a plurality of discharge regions distributed over the length of the discharge section, wherein the underside of the vehicle body is streamlined to create an air flow region of maximum air speed between the vehicle underside and the ground and wherein the discharge regions discharge exhaust gases into the latter air flow region.

In accordance with a second aspect of the invention, there is provided a motor vehicle driven by an internal combustion engine having an exhaust system, wherein the discharge section of the exhaust system from which the engine exhaust gases are discharged into the ambient atmosphere is elongate, extends transversely to the direction of motion of the vehicle and comprises a plurality of discharge regions distributed over the length of the discharge section, wherein the vehicle is fitted with a hollow rear spoiler the inner chamber of which is connected to the engine exhaust system, the discharge openings being formed in the spoiler to discharge the exhaust gases into the turbulent regions of the air slipstream near the spoiler.

In accordance with a third aspect of the invention, there is provided a motor vehicle driven by an internal combustion engine having an exhaust system, wherein the discharge section of the exhaust system from which the engine exhaust gases are discharged into the ambient atmosphere is elongate, extends transversely to the direction of motion of the vehicle and comprises a plurality of discharge regions distributed over the length of the discharge section, wherein the vehicle is fitted with a hollow rear bumper the inner chamber of which is connected to the engine exhaust system, the discharge openings being formed in the rear bumper to discharge the exhaust gases into the turbulent regions of the air slipstream near the rear bumper.

Brief description of the drawings The invention will now be described further, by way of example, with reference to the accompanying drawings, in which : Figure 1 shows a vehicle exhaust system having a transverse discharge section with openings distributed over its length, and Figures 2,3 and 4 each show a sketch of a vehicle in accordance with a respective one of the three aspects of the present invention.

Detailed description of the preferred embodiments Figure 1 shows an exhaust pipe 10 having a silencer (or muffler) 12 and a discharge pipe 14. The discharge section 20 of the pipe 14 is elongate and bent to extend transversely to the direction of motion of the vehicle and its slipstream represented by the long arrow. The end 22 of the discharge section is blocked so that the exhaust gases are all discharged from openings 24 distributed over the length of the transverse section 20. Such exhaust pipe has already been proposed in GB pat. application No. 9822484.3.

The invention seeks to position the transverse section 20 of the exhaust pipe at positions that take advantage of the aerodynamics of the vehicle body in order to improve mixing of the exhaust gases with ambient air.

In the case of the embodiment of Figure 2, the floor pan 32 of the vehicle 30 is streamlined to create high relative air speed under the vehicle and the discharge section 20 is located preferably at the position of maximum air speed. As illustrated it is desirable for the floor pan to form a venturi and for the exhaust gases to be discharged into the throat of the venturi. This construction has the advantage of increasing the mixing of the exhaust gases with ambient air before they reach the wake region of the vehicle thereby minimising the residence time of the exhaust gases in regions of low dilution. It has previously been appreciated that such prolonged residence times in regions of low dilution favour the formation of nano-particles.

In the embodiment of Figure 3, the vehicle 30 is fitted with a spoiler 33 and the transverse section 20 of the exhaust pipe is located in the spoiler 33 to discharge the exhaust gases into the turbulent regions created by the spoiler 33.

Another region of natural turbulence is at the edge of the rear bumper 34 of the vehicle 30 as shown in Figure 4.

It is possible to integrate the transverse section 20 of the exhaust pipe into the cross-section of the rear bumper 34.

The discharge openings should preferably be angled downwards to minimise the proportion of the exhaust gases directly entering into the wake region behind the vehicle 30.

Claims

1. A motor vehicle driven by an internal combustion engine having an exhaust system, wherein the discharge section of the exhaust system from which the engine exhaust gases are discharged into the ambient atmosphere is elongate, extends transversely to the direction of motion of the vehicle and comprises a plurality of discharge regions distributed over the length of the discharge section, wherein the underside of the vehicle body is streamlined to create an air flow region of maximum air speed between the vehicle underside and the ground and wherein the discharge regions discharge exhaust gases into the latter air flow region.

2. A motor vehicle driven by an internal combustion engine having an exhaust system, wherein the discharge section of the exhaust system from which the engine exhaust gases are discharged into the ambient atmosphere is elongate, extends transversely to the direction of motion of the vehicle and comprises a plurality of discharge regions distributed over the length of the discharge section, wherein the vehicle is fitted with a hollow rear spoiler the inner chamber of which is connected to the engine exhaust system, the discharge openings being formed in the spoiler to discharge the exhaust gases into the turbulent regions of the air slipstream near the spoiler.

3. A motor vehicle driven by an internal combustion engine having an exhaust system, wherein the discharge section of the exhaust system from which the engine exhaust gases are discharged into the ambient atmosphere is elongate, extends transversely to the direction of motion of the vehicle and comprises a plurality of discharge regions distributed over the length of the discharge section, wherein the vehicle is fitted with a hollow rear bumper the inner chamber of which is connected to the engine exhaust system, the discharge openings being formed in the rear bumper to discharge the exhaust gases into the turbulent regions of the air slipstream near the rear bumper.

4. A motor vehicle having an exhaust system constructed and arranged substantially as herein described with reference to and as illustrated in Figure 2, Figure 3 or Figure 4 of the accompanying drawings.