Method and device for preheating an engine or an engine intake air

The present invention provides an engine intake air preheating device having PA0 (A) an intake air preheater for preheating air to be fed into an engine, the preheater including a first metal hydride and being disposed within an intake air feeding tube for heat exchange with the intake air, PA0 (B) a hydrogen storage container including hydrogen or a second metal hydride, and PA0 (C) a pipe having a valve and connecting the intake air preheater to the hydrogen storage container so that hydrogen can move between them; and also an engine preheating device having PA0 (A') an engine preheater for preheating an engine, the preheater including a first metal hydride and being mounted on the engine for heat-exchange with the engine, PA0 (B) the hydrogen storage container, and PA0 (C) the pipe. There is also provided a method for preheating intake air at the time of starting the engine using an engine intake air preheating device such as the one according to the present invention.

This invention relates to a method and a device for pre-heating an engine 
or an engine intake air. More specifically, this invention relates to a 
method and a device for pre-heating an engine or an engine intake air 
using as a heat source the heat which is released from a hydrogen 
absorbing-dissolving material when it absorbs hydrogen. 
Generally, in cold districts or in the early morning in the wintertime in 
other districts as well, the temperature goes down below the freezing 
point. At such a time, it takes time to start an engine, and some time 
period is required until the inside of a car is warmed up full after the 
starting of the engine. 
In particular, the starting of a diesel engine is effected not by the spark 
ignition method involving using an ignition plug, but by the compression 
ignition method which comprises compressing air in a cylinder to a 
compression ratio of 16-24 to elevate its temperature to 
600.degree.-800.degree. C., and jetting a fuel oil into the cylinder to 
ignite and burn the fuel oil. Hence, the starting of the diesel engine 
essentially requires preheating the intake air to a predetermined 
temperature. It has been the previous practice to pre-heat air to be 
supplied to an engine by using an electric heater having a battery as a 
power supply. The capacity of the battery, however, is not high enough to 
pre-heat the intake air rapidly. On the other hand, increasing the size of 
the battery results in an extreme increase in its weight. 
Some period of time is required to warm the inside of a car after the 
starting of the engine until the driver and passengers become comfortable. 
To shorten the warming time, it has been proposed to warm the inside of 
the car by burning a fuel in a burner or electrically heating it by a 
heating coil or the like. This also requires a fuel or electrical energy. 
A method was previously proposed in which an automobile is warmed by 
transferring hydrogen from a low temperature hydride storage tank to a 
high temperature hydride storage tank to generate heat without the need 
for a fuel or an electrical energy, and utilizing the resulting heat for 
heating cooling water or the space inside the car (see Japanese Laid-Open 
Patent Publication No. 160,288/1980). 
This Japanese patent document, however, gives no description or suggestion 
even of the possibility of using the heat generated by hydrogn transfer 
for preheating an engine or an engine intake air. 
It is an object of this invention therefore to provide a method and a 
device for preheating an engine or an engine intake air by rapidly 
preheating the engine itself or the engine intake air in cold districts or 
in the early morning in the wintertime and thus facilitating the starting 
of the engine. 
Another object of this invention is to provide an economical method and 
device in which an engine or an engine intake air is preheated by the heat 
generated during the absorption of hydrogen by a metal hydride to 
facilitate the starting of the engine, and in which the hydrogen absorbed 
during a period from the starting of the engine until its stopping is 
released from the metal hydride and the hydrogen is stored to use it for 
preheating the engine or the engine intake air at the time of the next 
starting of the engine. 
Still other objects and advantages of this invention will become apparent 
from the following description. 
These objects and advantages of this invention are achieved in accordance 
with this invention by a method for preheating an intake air at the time 
of starting an engine, which comprises 
(1) feeding hydrogen from a hydrogen storage container into an intake air 
preheater including a first metal hydride, said hydrogen having a pressure 
higher than the hydrogen equilibrium absorption pressure of the first 
metal hydride, to thereby cause hydrogen to be absorbed by the first metal 
hydride and elevate the temperature of the intake air preheater by the 
heat generated at the time of absorption, 
(2) heat-exchangeably contacting air to be fed into an engine with the 
intake air preheater kept at the elevated temperature to thereby elevate 
the temperature of the intake air, 
(3) starting the engine by using the intake air having the elevated 
temperature, and 
(4) heating the first metal hydride during the operation of the engine or 
during the time period from the stopping of the engine to the next 
starting of the engine to thereby release hydrogen, and storing the 
released hydrogen as hydrogen having a higher pressure than the hydrogen 
equilibrium absorption pressure of the first metal hydride or as a second 
metal hydride having a higher hydrogen equilibrium absorption pressure 
than the hydrogen dissociation pressure of the first metal hydride. 
As a device suitable for practicing the method of this invention, the 
present invention provides an engine intake air preheating device 
comprising 
(A) an intake air preheater for preheating air to be fed into an engine, 
said preheater including a first metal hydride and being disposed within 
an intake air feeding tube for heat exchange with the intake air, 
(B) a hydrogen storage container including hydrogen having a higher 
pressure than the hydrogen absorption pressure of the first metal hydride 
or a second metal hydride having a higher hydrogen dissociation pressure 
than the hydrogen absorption pressure of the first metal hydride in an 
operating temperature range, and 
(C) a pipe having a valve and connecting said intake air preheater to said 
hydrogen storage container so that hydrogen can move between them.

With reference to FIGS. 1 and 2, the principle of preheating intake air in 
accordance with this invention will be described. 
According to this invention, the intake air preheater includes a first 
metal hydride, and hydrogen having a pressure higher than the hydrogen 
equilibrium absorption pressure of the first metal hydride is supplied to 
the first metal hydride. The hydrogen is fed from hydrogen stored in the 
hydrogen storage container or from a second metal hydride in the storage 
container which has a higher hydrogen equilibrium dissociation pressure 
than the hydrogen absorption pressure of the first metal hydride at the 
operating temperatures. 
FIG. 1 is a cycle diagram for the case in which hydrogen is stored in the 
hydrogen storage container, and FIG. 2 is a cycle diagram for the case in 
which the second metal hydride is stored in the hydrogen storage 
container. In FIGS. 1 and 2, the abscissa represents the reciprocal of the 
absolute temperature T, and the ordinate, the natural logarithm of the 
hydrogen equilibrium pressure P of the metal hydride. In FIG. 1, a first 
metal hydride MH1 included in the intake air preheater has a lower 
hydrogen equilibrium absorption pressure Pb than the hydrogen pressure P 
of the inside of the hydrogen storage container at the preheating 
temperature Tb of the intake air in the intake air feed tube at the time 
of starting the engine, and a higher hydrogen equilibrium dissociation 
pressure Pa than the hydrogen pressure P of the hydrogen storage container 
at the temperature Ta of the intake air during normal operation. 
Thus, when hydrogen having the pressure P is supplied to the first metal 
hydride MH1 at the time of starting the engine, MH1 absorbs hydrogen to 
generate heat. This heat warms the intake air which makes 
heat-exchangeable contact with the intake air preheater including MH1, and 
elevates the temperature of the intake air to Tb (heating step). On the 
other hand, at the temperature Ta of the intake air during normal 
operation after the starting of the engine, the hydrogen equilibrium 
dissociation pressure Pa of MH1 is higher than the hydrogen pressure P. 
Hence, MH1 releases hydrogen and forms hydrogen for use in the next 
starting of the engine (preparatory step). 
The first metal hydride MH1 included in the intake air preheater in FIG. 2 
has a lower hydrogen equilibrium absorption pressure Pd than the hydrogen 
equilibrium dissociation pressure at atmospheric temperature Tc of the 
second metal hydride MH2 included in the hydrogen storage container at the 
preheating temperature Td at the time of starting the engine. On the other 
hand, at the temperature Ta of the intake air during normal operation, the 
first metal hydride MH1 has a higher hydrogen equilibrium dissociation 
pressure Pa than the hydrogen equilibrium absorption pressure at the 
ambient temperature Tb of MH2. 
Accordingly, at the time of starting the engine, hydrogen is fed to the 
first metal hydride MH1 from the second metal hydride MH2, and MH1 absorbs 
hydrogen and generates heat. This heat warms the intake air which makes 
heat-exchangeable contact with the intake air preheater including MH1 and 
elevates the temperature of the intake air to Td (heating step). 
On the other hand, since after the starting of the engine, the hydrogen 
equilibrium dissociation pressure Pa of MH1 at the intake air temperature 
Ta during normal operation is higher than the hydrogen equilibrium 
absorption pressure of MH2 at the ambient temperature Tb, MH1 releases 
hydrogen endothermically. The released hydrogen is absorbed by MH2 for use 
in the next starting of the engine (preparatory step). 
FIG. 3 is a view showing the concept of the engine intake air preheating 
device in accordance with this invention. In an intake air feeding tube 3 
for feeding air to an engine 2 from a turbocharger 1, an intake air 
preheater 4 including the first metal hydride MH1 is mounted for 
heat-exchange with the air to be taken into the engine. A hydrogen storage 
container 6 is connected to the preheater through a pipe 5. Hydrogen is 
included in the hydrogen storage container 6. Or a second metal hydride 
(MH2) having a higher hydrogen equilibrium dissociation pressure than MH1 
in an operating temperature range is included in the hydrogen storage 
container 6. By a hydrogen stream flowing valve 7 in the pipe 5, the 
hydrogen storage container 6 communicates with the intake air preheater 4 
during the heating step and the preparatory step carried out as stated 
hereinabove. The hydrogen storage container 6 is disposed at a suitable 
position of a car body, and is in heat exchange relationship with the 
outer atmosphere or with the car body. 
FIG. 4 is a view showing the concept of another embodiment of the device in 
accordance with this invention, in which the same members of the device 
are designated by the same reference numerals as in FIG. 3. It will be 
easily understood that this embodiment differs from the device shown in 
FIG. 3 in that the intake air feed tube 3 is divided into two. 
Specifically, the intake air feed tube 3 is divided into an intake air 
preheating tube 8 and an intake air control tube 9. The same intake air 
preheater 4 as in the device of FIG. 3 is mounted on the intake air 
preheating tube 8. The air intake control tube 9 has a control valve 10 
for controlling the flow of the intake air from the turbocharger 1 to the 
engine. During the starting of the engine, the control valve 10 is closed 
to pass the intake air forcibly through the intake air preheating tube to 
preheat the intake air. After the engine has attained a normal operating 
condition, the control valve 10 is opened to pass the intake air without a 
pressure drop. As required, this control valve may be a manually operable 
valve or a solenoid valve. 
FIG. 5 is a view showing the concept of still another embodiment of the 
device in accordance with this invention, in which the exhaust gas of the 
engine is used as a heat source for heating the metal hydride in the 
intake air preheater during the preparatory step. A branched tube 3a from 
the intake air feed tube 3 leading to the engine 2 is connected to a 
branched tube 18b from an engine exhaust tube 18. Another branched tube 3b 
from the intake air feed tube 3 is connected to another branched tube 18a 
from the engine exhaust tube 18. Furthermore, an associating tube 17 is 
formed between the pair of branched tubes 3a and 3b In order that the 
intake air and the engine exhaust gas may flow into the associating tube 
17, control valves 19 and 20 in the engine exhaust tube 18 and the intake 
air feed tube 3, control valves 21 and 22 in the branched tubes 3a and 3b 
and control valves 24 and 23 in the branched tubes 18a and 18b are 
disposed respectively in such a manner that they can be opened and closed. 
The intake air preheater 4 is further disposed in the associating tube 17. 
In the same way as above, the hydrogen storage container 6 is connected to 
the intake air preheater 4 by means of the pipe 5 having the hydrogen flow 
valve 7. 
In the heating step in accordance with this device, the control valve 19 in 
the engine exhaust tube 18 is opened and the control valves 24 and 23 in 
the branched tubes 18a and 18b are closed. At the same time, the control 
valve 20 in the intake air feed tube 3 is closed and the control valves 21 
and 22 in the branched tubes 18a and 18b are opened. These are shown by 
broken lines at the control valves. As a result, the intake air flows into 
the associating tube 17 and is heated by the intake air preheater 4. On 
the other hand, in the preparatory step, the control valve 19 in the 
engine exhaust tube 18 is closed and the control valves 23 and 24 at the 
branched tubes 18a and 18b are opened. At the same time, the control valve 
20 in the intake air feed tube 3 is opened, and the control valves 21 and 
22 in the branched tubes 3a and 3b are closed. These are shown by the 
solid lines in the control valves. As a result, the exhaust gas flows into 
the associating tube 17 and heats the intake air preheater 4. 
It is believed that the foregoing description with reference to FIGS. 3 to 
5 clarifies the relation of the method and device of this invention to 
FIGS. 1 and 2. A further description will, however, be made with reference 
to the device of FIG. 3 as an example. In relation to FIG. 1, the device 
of FIG. 3 will be described. When the hydrogen flow valve 7 is opened at 
the time of starting the engine in order to perform the heating step, 
hydrogen in the hydrogen storage container 6 flows into the intake air 
preheater 4. MH1 absorbs this hydrogen at temperature Tb and generates 
heat and thus heats the intake air in the intake air feed tube 3. In the 
heating step, the hydrogen pressure in the hydrogen storage container is 
decreased to some extent. When the engine has reached a normal operating 
conditions in this manner, the intake air elevated to temperature Ta by 
being compressed by the turbocharger 1 has a higher temperature than the 
intake air preheater 4 and the intake air preheater is then heated. Thus, 
MH1 included in the preheater endothermically releases hydrogen at 
temperature Ta. This hydrogen returns to the hydrogen storage container 6 
via the pipe 5 and gains the original pressure. After this preparatory 
step, the hydrogen flow valve 7 is closed, and the device is ready for the 
next starting of the engine. 
Now, in relation to FIG. 2, the device of FIG. 3 will be described. When in 
the heating step, the hydrogen flow valve 7 is opened at the time of 
starting the engine, MH2 in the hydrogen storage container 6 releases 
hydrogen while absorbing heat from the atmosphere at temperature Tc. This 
hydrogen is absorbed by MH1 in the intake air preheating tube 4 at 
temperature Td to generate heat. In the preparatory step, MH1 in the 
intake air preheater 4 is heated by the compressed intake air at 
temperature Ta from the turbocharger 1 which has reached an ordinary 
operating condition. As a result, MH1 releases hydrogen at temperature Ta, 
and this hydrogen is absorbed by MH2 at temperature Tb. The heat generated 
by MH2 at this time is dissipated into the atmosphere or the car body. 
Thereafter, the hydrogen flow valve 7 is closed, and the device is ready 
for the next starting of the engine. 
Accordingly, if the hydrogen flow valve 7 is constructed of a solenoid 
valve and adapted to be opened upon the starting of the engine and closed 
upon the stopping of the engine, the device of this invention can be 
easily operated without the need for any other control instrument. 
In the device of this invention, for example the device shown in FIG. 5, an 
electric heater (not shown) may be provided in the intake air preheater 4. 
In this case, hydrogen may be returned from MH1 to MH2 by the electric 
heater or by the aid of it. Hence, the preparatory step can be completed 
surely even if the running distance of the automobile is short. 
Furthermore, the metal hydride can be selected from a broad range of metal 
hydrides. 
FIG. 6 shows one embodiment of the principal parts of the intake air 
preheater in accordance with this invention. One or a plurality of 
cylindrical containers 11 are disposed within the intake air feed tube 3 
and fixed to each other or to the wall of the intake air feed tube. A 
metal hydride 13 is filled in the inside of each of the containers. The 
containers are connected to the hydrogen storage container 6 by means of 
the pipe 5 having the hydrogen flow valve 7. The spaces among the 
cylindrical containers 11 form passages 14 for the intake air. 
FIG. 7 shows another embodiment of the principal parts. Fins 15 are 
radially formed in the intake air feed tube 3, and the feed tube is formed 
in a multitubular structure with the individual tube members being 
concentric with each other. For example, as shown, a metal hydride 13 is 
filled in annular portions between tube member walls and the tube members 
are connected to the pipe 5. The other space portions form passages 16 for 
the intake air. 
In the foregoing description, air compressed and heated by the turbocharger 
or the engine exhaust gas is utilized as a heat source for heating the 
metal hydride MH2 in the intake air preheater in the preparatory step. It 
will be easily understood that when the device of this invention requires 
a heat source, the heat source is not limited to those stated above, and 
all heat generated by the operation of the engine can be utilized. 
Examples of such heat sources may be the engine body, the engine cooling 
water and the engine oil. 
Now, the device of this invention used for preheating an engine by the heat 
generated by a metal hydride at the time of absorbing hydrogen will be 
described. 
The device of this invention for preheating an engine comprises 
(A') an engine preheater for preheating an engine, said preheater including 
a first metal hydride and being mounted on the engine for heat-exchange 
with the engine, 
(B) a hydrogen storage container including hydrogen having a higher 
pressure than the hydrogen absorption pressure of the first metal hydride 
or a second metal hydride having a higher hydrogen dissociation pressure 
than the hydrogen absorption pressure of the first metal hydride in an 
operating temperature range, and 
(C) a pipe having a valve and connecting said intake air preheater to said 
hydrogen storage container so that hydrogen can move between them. 
The structure of the engine preheating device of this invention is the same 
as the engine intake air preheating device described above except that the 
structure (A') of the former differs from the structure (A) of the latter. 
Hence, the operating principle of the engine preheating device of this 
invention can be easily understood from the foregoing description given 
with reference to FIGS. 1 and 2 by reading "engine" for "intake air". 
FIG. 8 is a view showing the engine preheating device in accordance with 
this invention. An engine preheater 31 including a first metal hydride MH1 
is mounted on an engine in close contact with an engine head 32 so that it 
permits heat-exchange with the engine head 32. A hydrogen storage 
container 34 is connected to this preheater through a pipe 33. Hydrogen is 
filled in the hydrogen storage container 34, or it includes a second metal 
hydride MH2 having a higher hydrogen equilibrium dissociation pressure in 
the operating temperature range. The hydrogen storage container 34 is 
caused to communicate with the engine preheater 31 while the aforesaid 
heating step and the preparatory step are carried out by a hydrogen flow 
valve 35 of the pipe 33. The hydrogen storage container 34 is disposed at 
a suitable position of a car body and is in heat exchange relationship, 
for example, with the outer atmosphere or the car body. 
FIG. 9 is a view showing the concept of another embodiment of the device of 
this invention. The same members as in FIG. 8 are represented by the same 
reference numerals. It will be easily understood that a socalled heat pipe 
36 having good thermal conductivity is fixed closely to the engine head 
32, and the engine preheater 31 is connected to the heat pipe 36. 
Otherwise, the structure of the device is the same as the device shown in 
FIG. 8. Heat exchange between the engine preheater 31 and the engine head 
32 is carried out through the heat pipe 36. 
If the hydrogen flow valve is a solenoid valve and adapted to be opened 
upon the starting of the engine and closed upon the stopping of the 
engine, the engine preheater of the invention can be easily operated 
without the need for another controlling instrument as in the case of the 
engine intake air preheater of this invention. 
The operation of the intake air preheating device of this invention will be 
described specifically. 
When in the device which performs the operation shown in FIG. 1, 1 kg of 
LaNi.sub.5 was used as MH1 in the intake air preheater and the capacity of 
the hydrogen storage container was adjusted to 37 liters (Tb=about 
50.degree. C., Pb=about 6 atmospheres, Ta=about 70.degree. C., Pa=about 10 
atmospheres), the temperature of the intake air could be elevated to about 
15.degree. C. in several seconds (the temperature of the atmosphere at the 
time of starting the engine in the heating step was -25.degree. C.). When 
the intake air was preheated by jointly using a conventional electric 
heater capable of giving a temperature increase of 25.degree. C., it could 
be heated to about 40.degree. C. In the preparatory step, the intake air 
was compressed by the turbocharger and attained a temperature of 
50.degree. to 70.degree. C., hydrogen could be released from the metal 
hydride and the device was ready for the next starting of the engine. 
When in the device which performs the operation shown in FIG. 2, 1 kg of 
CeCo.sub.5 was used as MH1 and 1 kg of MmNi.sub.5 (Mm=misch metal) was 
used as MH2 (Tc=about -30.degree. `C., Tb=about 0.degree. C., Td=about 
30.degree. C., Ta=about 50.degree. C., Pd=about 1 atmosphere, Pa=about 10 
atmosphere), the temperature of the intake air could be elevated to about 
5.degree. C. within several seconds (the temperature of the atmosphere at 
the start of the engine was -25.degree. C.). When an electric heater was 
jointly used, the intake air could be heated to about 30.degree. C. After 
the engine attained a normal operating condition, MH1 in the intake air 
preheater could be heated by the intake air at 50.degree. to 70.degree. C. 
and hydrogen could be released from it. Hence, the device was ready for 
the next starting of the engine. 
Assuming that the weight of the engine required to be preheated was 50 kg 
and its heat capacity was 5 kcal/.degree.C., the operation of the engine 
preheating device of this invention will be specifically described below. 
When in the device which performs the operation shown in FIG. 1, 6 kg of 
ZrMn.sub.2 was used as MH1 in the engine preheater and the capacity of the 
hydrogen storage container was adjusted to 85 liters (Tb=about 30.degree. 
C., Pd=about 1 atmosphere, Ta=about 130.degree. C., Pa=about 10 
atmospheres), the temperature of the engine which was -25.degree. C. at 
the time of starting the engine in the heating step could be elevated to 
about 25.degree. C. within several seconds. In the preparatory step, the 
engine head attained a temperature of about 130.degree. C., and hydrogen 
could be easily released from the metal hydride. 
When in the device which performs the operation shown in FIG. 2, 6 kg of 
CaNi.sub.5 was used as MH1 and 6 kg of MmNi.sub.5 (mm=misch metal) was 
used as MH2 (Tc=about -25.degree. C., Tb=about 0.degree. C., Td=about 
30.degree. C., Ta=about 130.degree. C., Pd=about 1 atmosphere, Pa=about 10 
atmospheres), the temperature of the engine which was -25.degree. C. at 
the time of its starting could be elevated to about 25.degree. C. within 
several seconds. After the engine attained a normal operating condition, 
the engine head heated the MH1 in the preheater as described above, and 
hydrogen could be released from MH1. 
Preferred first metal hydrides for use in this invention include, for 
example, LaNi.sub.5-x Al.sub.x (1.gtoreq.x.gtoreq.0), CeCo.sub.5, 
ZrMn.sub.2 and CaNi.sub.5. Preferred second metal hydrides for use in this 
invention include, for example, MmNi.sub.5 (Mm=misch metal). 
The combination of the first metal hydride and the second metal hydride can 
be easily determined from the temperature dependences of the hydrogen 
equilibrium dissociation-absorption pressures of these metal hydrides. 
Since according to this invention, an engine or an engine intake air is 
preheated by utilizing a metal hydride which absorbs hydrogen, the device 
is light in weight and can perform preheating rapidly to a higher 
temperature. Accordingly, the device of the invention greatly facilitates 
the starting of engines in cold districts and in the early morning in the 
wintertime.