GB1577599A

GB1577599A - Method of and apparatus for the torque and smoke-emission properties of turbocharged diesel-engines

Info

Publication number: GB1577599A
Application number: GB49651/77A
Authority: GB
Original assignee: Autoipari Kutato Intezet
Current assignee: Autoipari Kutato Intezet
Priority date: 1976-12-03
Filing date: 1977-11-29
Publication date: 1980-10-29
Also published as: SE437402B; DE2753799C2; SE7713323L; DE2753799A1; FR2372968B1; JPS53102413A; FR2372968A1; HU179402B; CH631239A5; IT1097729B

Abstract

In an internal combustion engine a control valve (14) is arranged in the fresh air line (3) between the turbocompressor (5) of the turbocharger (11) and the intake opening of the cylinder. A turbocharger (11), the air delivery of which is equal to the fresh air demand of the engine (1) when the engine (1) is at full load and at half the rated speed of the engine (1), is adjusted to the engine (1). Within the said range of revolutions a pressure ratio defined by the admissible maximum combustion peak pressure can be observed, the amount of air delivered when the engine is at the rated speed exceeding the fresh air demand of the engine by up to 10%. The excess air delivered by the turbocompressor (5) is released by way of the automatic control valve (14) adjusted to the permissible maximum overcharging pressure. In order to achieve a uniform torque curve, tuned intake pressure charging is applied in the fresh air system, which charging is matched to that engine speed range in which the maximum combustion peak pressure could not be attained without the use of tuned intake pressure charging. <IMAGE>

Description

(54) METHOD OF, AND APPARATUS FOR, IMPROVING THE TORQUE AND SMOKE-EMISSION PROPERTIES OF TURBOCHARGED DIESEL-ENGINES (71) We, AUT6IPARI KUTATO INTÉZET, of Budapest XI, Csoka utca 5-7, Hungary, a body corporate organized under the laws of Hungary, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement::- This invention relates to a method of, and apparatus for, improving the torque and smoke emission properties of turbocharged diesel engines, the turbo-compressor of which provides maximal overcharging within the range of r.p.m. below the range of r.p.m. associated with the maximal torque of the suction engine, while above this range a regulating valve arranged in the fresh air delivery conduit is effective to discharge surplus air which is in excess of the air demand of the engine into a by-pass duct.

It is a well-known disadvantageous property of turbocharged diesel engines that the characteristic curves of turbocompressor delivery are not favourable, whether it is considered from the point of view of the air consumption of the piston engine, or the whole unit driven by the exhaust turbine.

The disadvantageous feature lies in that at a low number of revolutions, of the engine, the air delivered by the turbocharger is less than is required while at higher r.p.m., there is a risk of overcharging, and thermal overload of the engine due to the increased air delivery. In motor vehicle operation, due to the necessarily non-constant r.p.m., these disadvantageous features result in increased smoke and pollutant emission on acceleration.

Several proposals are known for eliminating these disadvantageous features of turbocharged engines but none has been entirely successful so far. Thus, in known solutions, there is provided in the exhaust manifold upstream of the exhaust turbine a by-pass duct closable by a valve which is controlled by a pressure-sensing device responsive to the pressure in the delivery conduit of the turbocompressor. When the output pressure of the turbocompressor exceeds a predetermined value, a part of the exhaust gas is passed into the by pass duct to by-pass the turbine. The drawback of this apparatus is that the throttle valve is disposed in the exhaust manifold where it is subjected to high temperatures and at higher engine r.p.m. the turbocharger cannot be operated in its best efficiency range; also, a part of the energy of the exhaust gas remains unutilised.

In another known apparatus the delivery conduit of the turbocompressor is connected to the section of the exhaust manifold upstream of the turbine and can be closed by valve means. Consequently, a part of the compressed air can be utilised for mixing with the exhaust gases or for supplying one of two turbines. Adjustment of the valve takes place either by a hand lever or in dependence on engine r.p.m. This method can only be used for large engines because of the cumbersome operation and maintenance and because of the use of two turbines.

In a further known apparatus it is sought to improve insufficient air delivery occurring at low r.p.m. by arranging that the delivery conduit of the turbocompressor discharges into a plenum connected to a resonance vessel by means of a resonance pipe, and short induction manifolds, the suction periods of which do not overlap to any significant extent, are connected to the resonance vessel. The natural resonance of the system is tuned to a suitably low number of revolutions of the engine so as to promote an increase in the otherwise insufficient delivery of the turbocharger. The use of this method has been limited partly by the magnitude of the effective resonance range and partly by the large dimensions of the apparatus, to the extent that in many motor vehicle applications the method and apparatus became impracticable.

An aim of the present invention is to develop a turbocharger which is so matched to a motor vehicle engine that its air delivery is better adapted to the fresh air consumption of the piston engine, and which (compared with the prior art) is simpler, more reliable, and can comply with requirements relating to smoke-emission.

A further aim of the invention has been to increase the available torque of internal combustion engines within the limits provided by thermal loads and strength requirements in the widest possible range of r.p.m.

Our invention is based on the discovery that a turbocharger should be used which can delivery a sufficient quantity of fresh air for overcharging at a low r.p.m., i.e. within the range of r.p.m. below that associated with the maximum torque of the suction engine, so that the engine is fully utilised up to reaching the maximum permissible combustion peak pressure, while in higher r.p.m.

ranges, the quantity of air exceeding the fresh air consumption of the engine can be vented through a regulating valve to the ambient atmosphere or used for other purposes.

According to one aspect of the present invention there is provided a method of improving the torque and smoke emission properties of turbocharged internal combustion piston engines with fuel injection e.g.

diesel engines, wherein there is a discharge valve in the fresh air conduit between the turbocompressor of the turbocharger and the suction inlets of the cylinders, the method comprising fitting a turbocharger to the engine the fresh air delivery of which corresponds in quantity with the fresh air demand of the engine at full load at or in the vicinity of one half of the rated engine r.p.m.

and at this engine r.p.m. it has a pressure ratio limited by the maximum permissible combustion peak pressure and wherein the turbocharger delivery exceeds the fresh air demand of the engine by not more than 10% at the rated engine r.p.m., with the excess air being dumped through an automatic regulating valve set to the maximum permissible overcharge pressure.

According to another aspect of the invention there is provided apparatus for performing the method set forth in the preceding paragraph, the apparatus comprising a turbocharger so selected that the air delivered by it equals the fresh air demand of the internal combustion engine at full load and at or near one-half the rated engine r.p.m., and at the said r.p.m. the pressure ratio of the turbocompressor approximates to the maximum permitted overcharge pressure which latter is restricted by the maximum permissible combustion peak pressure, while delivery of air within the range of the rated engine r.p.m. it is at most 10% higher than the fresh air demand of the engine, and an automatic regulating valve is arranged in the fresh air conduit and is adjusted to the maximal overcharge pressure.

In a preferred embodiment, the delivery conduit of the turbocompressor is connected to discharge into a collecting vessel or plenum which is connected via a resonance duct to a resonance vessel which in turn is coupled to the induction manifolds of preferably three, or at most four, cylinders the suction periods of which do not overlap to any significant extent, the resonance of the whole system is tuned to an engine r.p.m. at which without the resonance charge the maximal permissible peak pressure could not have been reached.

By using this invention it is achieved that, in comparison with known turbochargers, for a given internal combustion engine a smaller, lighter and cheaper turbocharger can be used and at one-half the rated engine r.p.m. maximum torque is attained, the value of which can be kept approximately constant up to 3/4 of the rated engine r.p.m.

Under these circumstances, a turbocharger can be selected so that the quantity of compressed air discharged into the atmosphere does not exceed 6-10% of the quantity of air delivered by the turbocompressor whereby the economic operation of the engine is not significantly impaired.

A result worthy of attention of the maximal permissible turbocharging at a low r.p.m. is that the pumping work of the internal combustion engine becomes positive in a wide r.p.m. range and thus the torque is also increased.

It is a well known fact that the combustion peak pressure of piston engines can be displayed on a curve, the slope of which varies in dependence on the r.p.m.

Not even the present invention can achieve complete uniformity of the peak pressure curve, but on the other hand, according to a further embodiment of this invention, an increase of peak pressure values below the permissible limit becomes possible. This is of course only then sensible when it is accompanied by an increase in the effective mean pressure i.e. an increase in torque.As a complement to turbocharging, resonance charging tuned to the abovementioned r.p.m. range is used; constructionally, this is done by providing a collecting or plenum vessel downstream of the turbo-compressor and by resonance pipes connecting the vessel with a resonance tes- sel, the latter being connected via induction manifolds of sufficiently short length to prevent oscillations to the individual cylinders the suction periods of which are arranged not to overlap each other to any significant extent.

By using the invention, emission in particular the emission of black smoke can be improved, since the relatively small turbocharger can better follow the varying operational conditions of the engine and its varying fresh air demand, especially during acceleration, within low r.p.m. ranges compared with values provided by manufacturers of turbochargers, the mass of the rotary part of the turbocharger according to the invention, matched to an engine of given air demand, is approximately 50% less, and as a consequence, it is more suitable for operation with varying r.p.m.

In order to improve visible smoke emission, the excess air dumped by the valve is passed into the exhaust manifold arranged behind the turbine.

A diesel engine charged by the method according to the invention shows extremely advantageous features in high altitude operation, in particular at sub-atmospheric pressures, i.e. below 2 kp/cm2.

By using conventional charging methods, decreases in the maximal nominal capacity associated with zero altitude can be knept to approximately 20% when the altitude is 5,000 m, but on partial load and at lower r.p.m. of the engine the decrease in output and torque is respectively far in excess of 20%. With engines charged in accordance with the invention, the torque of the engine can be significantly improved in the low r.p.m. range even at high altitudes, i.e. the torque will decrease to a lesser extent as a function of altitude.

The invention will be described in detail by way of two preferred embodiments, where in the second example turbocharging as well as dynamic charging are used for a diesel engine.

These embodiments of the invention will be described with the aid of the accompanying drawings, wherein: Figure 1 shows a schematic arrangement of a six-cylinder in-line diesel engine with turbocharging, Figure 2 illustrates a schematic arrangement of a six-cylinder in-line diesel engine operated with dynamic induction manifold charging and provided with resonance vessels, Figure 3 shows in an enlarged crosssectional view the valve used for the regulation of the air intake in the embodiment of Figures 1 and 2, Figure 4 is a graph of the lag of turbochargers with different characteristic curves when a turbocharged diesel engine is accelerated, Figure 5 is a graph of the behaviour of the excess air factor of different turbochargers having different characteristic curves, when acceleration takes place, and Figure 6 is a graph of the changes of smoke emission on acceleration, when using turbochargers with different characteristic curves.

Figure 1 illustrates a schematic arrangement of a turbocharged in-line six-cylinder diesel engine according to the invention.

Each of the cylinders I-VI of the engine 1 has a suction conduit 2 connected to the common induction manifold 3 through a plenum 4, and the induction manifold 3 is connected to the pressure or delivery pipe 6 of the turbocompressor 5.

The exhaust pipes 7 of the cylinders I-VI are connected to a common exhaust manifold 8 which is connected to the inlet 10 of a gas turbine 9. The rotary parts turbocompressor 5 and the turbine 9 are mounted on a common shaft and together form a turbocharger unit 11. A nonillustrated air filter is arranged upstream of the air suction conduit 12 of the turbocompressor 5. The exhaust manifold 13 of the turbocharger is connected to the outlet of the turbine 9.

In the common induction manifold 3 there is a regulating valve 14 the construction of which is illustrated in greater detail in Figure 3. Air can be discharged from the common induction manifold 3 into the exhaust manifold 13 via the regulating valve 14, by way of a connecting pipe 15.

The regulating valve 14 is formed as a pressure regulating or dump valve to prevent a pre-adjusted maximal pressure from being exceeded by dumping or venting excess air.

The turbocharger 11 and the engine 1 are so selected and co-ordinated that they should be capable of being used in road vehicles within a wide range of r.p.m. with the greatest possible torque. In order to comply with this requirement the aim in this embodiment has been to maximise the peak combustion pressure within the widest possible r.p.m. range. The turbocharger 11 was therefore selected so that the turbocompressor 5 could deliver a sufficient quantity of air at the lowest possible r.p.m. but at higher r.p.m., especially at the rated engine r.p.m.

the quantity of air discharged or dumped should not significantly impair the efficiency of the internal combustion engine.

In our example the rated number of revolution of a lorry-engine of 10 litres cylinder capacity amounts to 2200 r.p.m.

The maximum torque of an engine charge in the known manner occurs at 1600 r.p.m.

and is approximately constant in the range of 1400 to 1800 r.p.m. With a turbocharger according to our invention, the maximum pressure condition and maximum torque are reached at a lower value, namely 1200 r.p.m. The regulating valve 14 is arranged to open at about 1600 r.p.m. and maintains maximum charging pressure in the common induction manifold 3. At rated engine r.p.m., where the regulating valve 14 dumps the maximum quantity of air, that quantity is no more than 8% of the air quantity deli- vered by the turbocompressor 5. This air quantity is delivered through the connecting pipe 15 into the exhaust manifold 13, whereby the smoke emission factor of the engine is considerably improved.

The attainment of maximal combustion peak pressure in the widest possible range of r.p.m. by the arrangement of Figure 1 is restricted e.g. by mechanical losses due to pumping, as a function of r.p.m. In a further embodiment, schematically shown in Figure 2, these restrictions are reduced or eliminated by providing a suction system suitable for resonance-charging wherein the most effective charging range of r.p.m. is adjusted to the range of r.p.m. where compensation is required. The process of resonance charging, and apparatus for carrying it out, have been described in Hungarian patent No.

161,323 (=DE-AS 1 93515 and U.S.

Patent Specification No. 3,796,048). In order to reach the maximum loadability of the diesel engine described above, the highest resonance charge is set to the range between 1300 and 1500 r.p.m.

In the Figure 2 embodiment, the turbocompressor 5 is connected via a connecting tube 15, to a collecting vessel or plenum 16 which in turn is connected to each of two resonance vessels 18 by a respective resonance pipe 17. Each resonance vessel 18 is connected to three of the six in-line cylinders via suction pipes 19. Efficient charging in the r.p.m. range of 200 to 400 r.p.m. can be achieved by selecting the volume of each resonance vessel 18 to be double the aggregate volume of the three cylinders connected to it, and by selecting the length of each resonance pipe 17 to be nine times its diameter. The cylinders connected to each common resonance vessel 18 are arranged so that their suction periods do not overlap to any significant extent.

The task of the regulating valve 14 is to prevent exceeding of the predetermined pressure value and it is arranged on the plenum 16. The air discharged thereby is passed via the connecting pipe 15 to a section of the exhaust manifold 13 which is downstream of the turbine.

The air regulating valve 14 is illustrated in detail in Figure 3. It has a valve body 20 secured to a coupling 21 that is screwconnected with the vessel 16, and another coupling 22 for connection the connecting pipe 15. A piston 23 is biased by a spring 24 seated in a recess 24a and bearing against an adjusting bolt 25. The annular surface 26 of the piston 23 of stepped configuration is arranged in a pressure space 27 connected by a duct 28 to the vessel 18. The pressure fluctuation of the valve is 0.02 kp/cm2, with the closing and opening pressure deviating from this value by 0.03 kp/cm2 only. The cross-sectional area of the opening closable by the piston 23 is linearly proportional to the displacement of the piston.

The advantageous features of the method and apparatus according to the invention appear principally with motor vehicles where the r.p.m. of the engine often changes and smoke emission is of great importance.

From the point of view of smoke formation, acceleration under load can be considered as most critical for turbocharged diesel-engines. When acceleration takes place, lagging of the turbocharger increases the tendency of smoke formation, while the r.p.m. of the engine increases. When the method according to the invention is used, the change in the r.p.m. of the turbocharger - the size of which is smaller than in the prior art - can more easily follow the change in engine r.p.m. during acceleration, hence the excess air factor of the engine will improve, while smoke formation diminishes.

The diagram shown in Figure 4 illustrates the change in turbocharger r.p.m. during acceleration, as a function of time, wherein: "n" indicates the r.p.m. of the turbocharger expressed as a % of the static operational state, T represents time, the curve "a" illustrates the change in the r.p.m. of the turbocharger of a diesel engine, charged in the known manner, while the curve "b" illustrates the change in the r.p.m. of the turbocharger of the same diesel engine charged in accordance with the invention, and the curve "m" indicates the change in the r.p.m. of the diesel engine.

Figure 4 shows the variation of the excess air factor as a function of time, with the engine r.p.m. changing in accordance with Figure 4 and using the same reference letters.

In Figure 6 the variation of the smoke index as a function of time has been illustrated, with the same reference letters as those of Figure 4.

In a non-illustrated embodiment, an air cooler is arranged between the automatic regulating valve and the suction inlets of the cylinder and the plenum, respectively.

WHAT WE CLAIM IS: 1. A method of improving the torque and smoke emission properties of turbocharged internal-combustion pistonengines with fuel injection e.g. dieselengines, wherein there is a discharge valve

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

pressure condition and maximum torque are reached at a lower value, namely 1200 r.p.m. The regulating valve 14 is arranged to open at about 1600 r.p.m. and maintains maximum charging pressure in the common induction manifold 3. At rated engine r.p.m., where the regulating valve 14 dumps the maximum quantity of air, that quantity is no more than 8% of the air quantity deli- vered by the turbocompressor 5. This air quantity is delivered through the connecting pipe 15 into the exhaust manifold 13, whereby the smoke emission factor of the engine is considerably improved.

The attainment of maximal combustion peak pressure in the widest possible range of r.p.m. by the arrangement of Figure 1 is restricted e.g. by mechanical losses due to pumping, as a function of r.p.m. In a further embodiment, schematically shown in Figure 2, these restrictions are reduced or eliminated by providing a suction system suitable for resonance-charging wherein the most effective charging range of r.p.m. is adjusted to the range of r.p.m. where compensation is required. The process of resonance charging, and apparatus for carrying it out, have been described in Hungarian patent No.

161,323 (=DE-AS 1 93515 and U.S.

Patent Specification No. 3,796,048). In order to reach the maximum loadability of the diesel engine described above, the highest resonance charge is set to the range between 1300 and 1500 r.p.m.

In the Figure 2 embodiment, the turbocompressor 5 is connected via a connecting tube 15, to a collecting vessel or plenum

16 which in turn is connected to each of two resonance vessels 18 by a respective resonance pipe 17. Each resonance vessel 18 is connected to three of the six in-line cylinders via suction pipes 19. Efficient charging in the r.p.m. range of 200 to 400 r.p.m. can be achieved by selecting the volume of each resonance vessel 18 to be double the aggregate volume of the three cylinders connected to it, and by selecting the length of each resonance pipe 17 to be nine times its diameter. The cylinders connected to each common resonance vessel 18 are arranged so that their suction periods do not overlap to any significant extent.

The task of the regulating valve 14 is to prevent exceeding of the predetermined pressure value and it is arranged on the plenum 16. The air discharged thereby is passed via the connecting pipe 15 to a section of the exhaust manifold 13 which is downstream of the turbine.

The air regulating valve 14 is illustrated in detail in Figure 3. It has a valve body 20 secured to a coupling 21 that is screwconnected with the vessel 16, and another coupling 22 for connection the connecting pipe 15. A piston 23 is biased by a spring 24 seated in a recess 24a and bearing against an adjusting bolt 25. The annular surface 26 of the piston 23 of stepped configuration is arranged in a pressure space 27 connected by a duct 28 to the vessel 18. The pressure fluctuation of the valve is 0.02 kp/cm2, with the closing and opening pressure deviating from this value by 0.03 kp/cm2 only. The cross-sectional area of the opening closable by the piston 23 is linearly proportional to the displacement of the piston.

The advantageous features of the method and apparatus according to the invention appear principally with motor vehicles where the r.p.m. of the engine often changes and smoke emission is of great importance.

From the point of view of smoke formation, acceleration under load can be considered as most critical for turbocharged diesel-engines. When acceleration takes place, lagging of the turbocharger increases the tendency of smoke formation, while the r.p.m. of the engine increases. When the method according to the invention is used, the change in the r.p.m. of the turbocharger - the size of which is smaller than in the prior art - can more easily follow the change in engine r.p.m. during acceleration, hence the excess air factor of the engine will improve, while smoke formation diminishes.

The diagram shown in Figure 4 illustrates the change in turbocharger r.p.m. during acceleration, as a function of time, wherein: "n" indicates the r.p.m. of the turbocharger expressed as a % of the static operational state, T represents time, the curve "a" illustrates the change in the r.p.m. of the turbocharger of a diesel engine, charged in the known manner, while the curve "b" illustrates the change in the r.p.m. of the turbocharger of the same diesel engine charged in accordance with the invention, and the curve "m" indicates the change in the r.p.m. of the diesel engine.

Figure 4 shows the variation of the excess air factor as a function of time, with the engine r.p.m. changing in accordance with Figure 4 and using the same reference letters.

In Figure 6 the variation of the smoke index as a function of time has been illustrated, with the same reference letters as those of Figure 4.

In a non-illustrated embodiment, an air cooler is arranged between the automatic regulating valve and the suction inlets of the cylinder and the plenum, respectively.

WHAT WE CLAIM IS: 1. A method of improving the torque and smoke emission properties of turbocharged internal-combustion pistonengines with fuel injection e.g. dieselengines, wherein there is a discharge valve

in the fresh air conduit between the turbocompressor of the turbocharger and the suction inlets of the cylinders, the method comprising fitting a turbocharger to the engine the fresh air delivery of which corresponds in quantity with the fresh air demand of the engine at full load at or in the vicinity of one-half of the rated engine r.p.m. and at this engine r.p.m. it has a pressure ratio limited by the maximum permissible combustion peak pressure and wherein the turbocharger delivery exceeds the fresh air demand of the engine by not more than 10% at the rated engine r.p.m., with the excess air being dumped through an automatic regulating valve set to the maximum permissible overcharge pressure.
2. Method as claimed in claim 1, wherein resonance charging is used in the fresh air system and is tuned to that range of engine r.p.m. in which maximal combustion peak pressure could not have been achieved without resonance charging.
3. Apparatus for performing the method according to claim 1, the apparatus comprising a turbocharger so selected that the air delivered by it equals the fresh air demand of the internal combustion engine at full load and at or near one-half the rated engine r.p.m., and at this r.p.m. the pressure ratio of the turbocompressor approximates to the maximum permitted overcharge pressure which latter is restricted by the maximum permissible combustion peak pressure, while delivery of air at the rated engine r.p.m. is at most 10% higher than the fresh air demand of the engine, and an automatic regulating valve is arranged in the fresh air conduit and is adjusted to the maximal overcharge pressure.
4. Apparatus as claimed in claim 3, wherein the induction manifold of the turbocompressor is connected to a plenum connected in turn to a resonance vessel by means of resonance pipes, said resonance vessel being coupled to the suction pipes of three or four cylinders the suction periods of which do not overlap to any significant extent and the resonance frequency of the fresh air system is adjusted to the engine r.p.m. at which the maximal combustion peak pressure could not have been achieved without the use of resonance charging.
5. Apparatus as claimed in claim 3 or 4, wherein a closing element of the automatic regulating valve is biased by a spring and the opening cross-sectional area is linearly proportional to the displacement of the closing element.
6. Apparatus as claimed in any of claims 3 to 5, wherein an air cooler is arranged between the automatic regulating valve and the suction inlets of the cylinders and the plenum, respectively.
7. A method according to claim 1 substantially as herein described with reference to and as shown in Figure 1 or Figure 2 of the accompanying drawings, taken in conjunction with Figures 3 to 6 thereof.
8. Apparatus according to claim 3, substantially as herein described with reference to and as shown in Figure 1 or Figure 2 of the accompanying drawings, taken in conjunction with Figures 3 to 6, thereof.
9. An internal combustion engine including a turbocharger and valve means constructed arranged and operating in use in accordance with any preceding clairn.