GB2305974A

GB2305974A - Reducing turbocharger lag

Info

Publication number: GB2305974A
Application number: GB9511830A
Authority: GB
Inventors: Adrian Graham Alford
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-06-10
Filing date: 1995-06-10
Publication date: 1997-04-23
Anticipated expiration: 2015-06-10
Also published as: GB9511830D0; GB2305974B

Abstract

For reducing turbocharger lag when increased power is required from a so-equipped engine 7, operating at part load, its compressor 8, is provided with nozzles or directing devices 3, designed to increase the speed of the rotor (9)(figures 1 and 2) or to rotate the charge entering the compressor. The devices 3, are supplied by recirculating compressed charged, via a distributor valve 2. A heat source such as a heat exchanger 4, (with a shunt 5, controlled by a distributor valve 6) using waste heat from exhaust gases, can heat the recirculating charge, thereby increasing the energy of the recirculated charge to further increase the rotational speed of the rotor or charge. Compressed air supplied to the engine 7, may pass through a cooler 10. The tendency of the turbocharger to surge may also be reduced.

Description

DEVICE FOR IMPROVING TURBOCHARGER DYNAMIC CHARACTERISTICS This invention relates to a turbocharger system for an internal combustion engine.

The problems with the use of the turbocharger with the internal combustion engine are well documented. One is known as "throttle lag and is caused by the low speed of the turbocharger rotor when the engine is operated at part load, combined with the energy required to overcome its inertia and accelerate the rotor to a speed where sufficient boost is created when increased power is required. If the rotor can be made to rotate at a greater speed at engine part load requirement by a reduction in compressor work and/or some additional work input, this problem could be alleviated very substantially.

Other benefits can accrue from this course of action, including a reduced tendency to turbocharger surge, and reduction of losses to throttling in the spark ignition engine.

According to the present invention the induction system of an internal combustion engine is provided with valve means to recirculate some portion of the compressed charge to the low pressure side of the compressor with some recovery of the energy expended in its compression by means of one or more nozzles or directing devices arranged so that the stream of this charge should impinge on the blades of the impellor so as to impart energy on them in their direction of rotation or cause the charge entering the compressor to rotate in the aforementioned direction.

This devised approach will have the effect of increasing the rotational speed of the rotor. A heat source, possibly a heat exchanger using waste heat from exhaust gases, can be provided to heat the recirculating charge between the two pressure regimes, the increase in the energy of this recirculated charge causing a further increase in the rotational speed of the rotor.

There will also be an additional effect due to the heating of the charge being delivered to the compressor and engine with further advantages accruing. Heated air, though requiring greater energy per unit mass for compression through a given ratio, has a lower energy requirement per unit volume for a similar compression, due to its lower density. It logically follows from this that for a given charge air density requirement at the engine, operating at some part of its rating, less throttling of the charge is required, reducing pumping losses at the engine and increasing turbocharger rotor speed.

With use with engines using variable valve timing as a load control means, the deficiency in charge temperature prior to ignition, which can have adverse effects on ignition and combustion, can be reduced.

Occurence of surge in the compressor can be reduced, due to the increase in mass flowrate through the compressor when this type of charge recirculation is operated, and a reduction in turbocharger pressure ratio is also anticipated within embodiments of the invention.

By means of a shunt and distributor valve to bypass the heat source of the recirculatory system and/or a shunt and distributor valve to bypass any chargecooler, the optimum temperature and density of charge reaching the cylinders can be provided.

A circumferentially split volute with more than one chamber where one chamber is arranged to be able to cause the charge to be compressed to a greater pressure - to be recirculated in any of the manners described in the above paragraphs - could be used within the context of this invention to achieve greater efficiency of operation.

Valve means can be provided to allow inflow of charge from the substantially atmospheric side of the induction system to the nozzle(s) or directing device(s) to increase the flow capacity of the compressor and decrease the incidence of compressor choke. The valve means shall be arranged to prevent compressed charge from venting through the recirculatory system to the substantially atmospheric side of the induction system.

One embodiment of the turbocharger system according to the invention is shown in figures 1, 2 and 3. Figure 1 shows a section of a turbocharger compressor 8 with impellor 9 and nozzles 3. Figure 2 shows another section through a similarly equiped compressor. Figure 3 shows the turbocharger system diagrammatically with reference numeral 1 indicating a turbocharger and 7 an internal combustion engine. The engine feed charge passes into the centrifugal compressor 8 from which it passes into inlet manifold 11. From here it passes to distributor valve 2 where some portion can be diverted to the charge recycling apparatus at engine part load. The remainder of the charge passes to the engine. The charge in the recycling apparatus then encounters distributor valve 6 where it can be directed in variable proportions to exhaust gas heat exchanger 4 and shunt 5. The charge then passes to nozzles 3 where it re-enters compressor 8, impingeing on the blades of the impellor, causing the impellor to rotate at greater speed.

Numeral 10 indicates a chargecooler.

Claims

1) A turbocharger provided with valve means to recirculate some portion of the compressed charge to the low pressure side of the compressor with some recovery of the energy expended in its compression by means of one or more nozzles or directing devices arranged so that the stream of this charge should impinge on the blades of the impellor so as to impart energy upon them in their direction of rotation or cause the charge entering the compressor to rotate in this direction.

2) A turbocharger as claimed in claim 1) characterised in that a heat source, possibly a heat exchanger using waste heat from exhaust gases, is provided to heat the recirculating charge between the two pressure regimes.

3) A turbocharger as claimed in claim 2) characterised in that a shunt and distributor valve are provided to bypass the heat source of the recirculatory system.

4) A turbocharger as claimed in claim 1), claim 2) or claim 3) characterised in that a circumferentially split volute with more than one chamber is used, where one chamber is arranged to be able to cause the charge to be compressed to a greater pressure for subsequent recirculation.

5) A turbocharger as claimed in claim 1), claim 2), claim 3) or claim 4) characterised in that valve means are provided to allow inflow of charge from the substantially atmospheric side of the induction system to the nozzles or directing devices. The valve means shall be arranged to prevent compressed charge from venting through the recirculatory system to the substantially atmospheric side of the induction system.