Method and apparatus for converting an alcohol into a motor fuel mixture

Abstract

A method and apparatus for converting an alcohol into a fuel mixture which consists of alcohol, ether and water and is suitable for operating a combustion engine, in particular an internal combustion engine in a motor vehicle, converts the alcohol into the fuel mixture in a reactor at a suitable reaction temperature. The mixing ratio of alcohol fraction, ether fraction and water fraction in the fuel mixture is adjusted by controlling at least one reaction parameter of a reaction taking place in the reactor.

Claims

1. A method for converting an alcohol into a fuel mixture which consists of alcohol, ether and water and is suitable for operating a combustion engine, comprising: converting, by a reaction using a catalyst, the alcohol into the fuel mixture in a reactor at a reaction temperature; and adjusting the mixing ratio of alcohol fraction, ether fraction and water fraction in the fuel mixture by controlling, by a control device, at least one reaction parameter of the reaction taking place in the reactor, wherein the at least one reaction parameter is controlled by the control device taking into account a first measurement signal indicating an operating parameter of an exhaust-gas aftertreatment system and a second measurement signal indicating an operating parameter of the combustion engine including at least one of speed, load, acceleration, cylinder pressure, and knocking.

2. The method according to claim 1, wherein the mixing ratio is adjusted by controlling at least one of the reaction temperature and the reaction pressure in the reactor.

3. The method according to claim 1, wherein the at least one reaction parameter is controlled by the control device taking into account the constitution of the alcohol to be converted.

4. The method according to claim 1, wherein the alcohol to be converted is a methanol-ethanol mixture.

5. The method according to claim 1, wherein the fuel mixture obtained according to said step of converting contains at least one of dimethyl ether and diethyl ether as ether fraction.

6. The method according to claim 1, further comprising the step of operating the combustion engine in the operating region of homogeneous compression ignition during said steps of converting and adjusting.

7. The method according to claim 1, the alcohol is converted into a fuel mixture such that the cetane number of the fuel mixture is above 50 during said step of converting.

8. The method according to claim 1, wherein the combustion engine is an internal combustion engine in a motor vehicle.

9. The method according to claim 1, wherein the second measurement signal indicates the speed of the combustion engine.

10. The method according to claim 1, wherein the second measurement signal indicates the cylinder pressure of the combustion engine.

11. The method according to claim 1, wherein the second measurement signal indicates knocking of the combustion engine.

12. The method according to claim 1, wherein the second measurement signal indicates the load of the combustion engine.

13. The method according to claim 1, wherein the second measurement signal indicates the acceleration of the combustion engine.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 shows a schematic depiction of an apparatus for converting an alcohol into a combustion engine fuel mixture according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(2) The apparatus has a tank 1 which contains an alcohol (methanol or ethanol for example) which is fed by a first pump P1 through a heating device 2 to a reactor 3. In reactor 3, the alcohol is converted at a suitable reaction temperature into a motor fuel mixture which is fed via a chamber 4 and a second pump P2 to a combustion engine 5. The combustion engine 5 is for this equipped with injection nozzles 6 to 9, via which the motor fuel mixture is injected into the combustion chambers of combustion engine 5.

(3) The apparatus depicted in FIG. 1 can more particularly be disposed in a motor vehicle with a diesel engine as combustion engine 5.

(4) In order that the motor fuel mixture supplied to combustion engine 5 has a mixing ratio of its alcohol, ether and water fractions which is suitable for combustion engine 5, heating device 2 heats the alcohol before entry into reactor 3 to a suitable temperature therefor. The process of heating is controlled by a control device 10 according to two or more operating parameters. Measurement signals representing different operating parameters are sent for this via measurement signal lines 11 to 13 to the control device 10 from sensors provided in reactor 3 and on combustion engine 5. The reaction temperature and the reaction pressure are received by control device 10 from reactor 3 as measurement signals on which the mixing ratio of alcohol, ether and water in the motor fuel mixture depends. Moreover, a knocking sensor 14 and a cylinder pressure sensor 15 send corresponding measurement signals to the control device 10 which together with further operating state signals, for example speed n, load and acceleration, characterize the current operating state of combustion engine 5. On the basis of these operating parameters of combustion engine 5, control device 10 can determine a suitable mixing ratio for the motor fuel mixture and effect an appropriate adjustment to the reaction in reactor 3.

(5) Heating device 2 in the depicted exemplary embodiment consists of an exhaust-gas heat exchanger 16 and an air heat exchanger 17. An exhaust-gas line 18 leads from combustion engine 5 through the exhaust-gas heat exchanger 16 and, inside the exhaust-gas heat exchanger 16, heats the alcohol likewise directed through the exhaust-gas heat exchanger 16. The heated alcohol passes from the exhaust-gas heat exchanger 16 to the air heat exchanger 17, where ambient air flowing therethrough can be used to cool the alcohol down to a desired temperature. Both the exhaust-gas heat exchanger 16 and the air heat exchanger 17 can be controlled heat exchangers, facilitating controlled heat transfer. For instance, a bypass control in exhaust-gas heat exchanger 16 can be used to ensure that only a certain proportion of the exhaust-gas stream is used to heat the alcohol flowing therethrough. In the case of air heat exchanger 17, controlled cooling of the alcohol flowing therethrough is possible by control device 10 controlling, for example, the air throughput through the air heat exchanger 17.

(6) It will be appreciated that a different heat transfer medium, such as water or oil (not depicted here), can also be used for heat exchanger 17 in place of air.

(7) The pressure in the reactor can be varied using control elements as well as the temperature. One way to do this is by changing the methanol quantity pumped by pump P1, for example by changing the speed or lift or by means of a variable throttle disposed on the suction side of pump P1. A further way is to use a pressure control valve on the pressure side of pump P1 to adjust the pressure in the reactor irrespective of the reactor temperature.

(8) The motor fuel mixture produced in reactor 3 can, if necessary, be aftertreated or intermediately stored in a chamber 4 downstream of reactor 3.