Method of carrying out a cycle in a piston internal combustion engine and a piston internal combustion engine

This invention relates to internal combustion engines (ICE) and concerns the problem of increasing the effective use of fuel in them. The piston ICE includes a housing with installed cylinders 1, pistons 2 and the air-fuel mixture preparation system which includes two-stage thermodynamic energy exchanger 5 with cooler 6, installed between the stages of the exchanger 5, and the outlet of the second stage is connected with heat-insulated receiver 7 whereas this receiver is connected with engine cylinders by means of the valves 8. The combustion chamber 9 may be installed between the receiver 7 and the cylinder 1. In order to reduce the losses the hot gas expansion is accomplished at first in engine cylinder 1 to obtain the highest possible useful work, and then in thermodynamic energy exchanger 5, in which the air is compressed to achieve the parameters of fuel combustion beginning, after that the compressed air is stored in the receiver 7 while keeping the air parameters and is used for mixture preparation when it is necessary. The air is compressed in two stages: in first stage with cooling in the cooler 6 and then with heat loss prevention resulting from the heat insulation of the receiver 7.

TECHNICS DOMAIN 
The invention relates to energy-transforming plants, namely relates to 
piston internal combustion engines (ICE), in which the energy of cylinder 
exhausted gases is used to compress fresh charges of air. 
BACKGROUND 
The analysis of ICE shows that the parameters of its working process are 
not sufficiently high. In particular, they are 10-20 times lower than the 
parameters of steam engines. The maximum pressures of working substance 
for ICE and steam engine are comparative, but the mean effective pressure 
related to the working stroke equals about 10 kg/cm.sup.2, and when 
related to volume displacement in a four-stroke working process equals 
only 2.5 kg/cm.sup.2. For a steam engine this characteristic reaches 50 
kg/cm.sup.2. 
The second substantial drawback of ICE is the incompatibility of the 
initial and final parameters of working substance. If at the beginning of 
compression, the pressure is equal 1 kg/cm.sup.2 and the temperature is 
equal 300K, then at the end of the process, i.e. during the discharge of 
exhaust gases in atmosphere, the pressure reaches 6 kg/cm.sup.2 and the 
temperature 1700K. When having such parameters there are great output 
losses of energy, substantial environment pollution and a complicated 
problem to silence exhaust noise of the engine operation. 
The third essential drawback of ICE is the imperfection of the working 
substance compression process. It should be noted that the energy to 
compress a working substance is taken from the working gases, i.e. there 
is an exchange of thermodynamic energy between the working gases and the 
air being compressed before a combustion of fuel in it. The losses 
peculiar to ICE mechanism arise because of this energy exchange, and these 
losses are doubled because the mechanical energy obtained from the working 
gases travels from a piston bottom to a flywheel and then back. 
The fourth drawback of majority of ICE is the discrepancy from an ideal 
compression process, which must proceed at first with intensive cooling 
and then at a second phase the adiabatically. Partly, the regulation of a 
heat transfer is realized by ceramic inserts, which insulate the cylinder 
walls and combustion chamber. Nevertheless, these inserts do not provide 
the intensive heat transfer at the first phase of a compression and 
improve only compression conditions at the second phase. 
There are many various technical solutions in which the gases obtained as a 
result of air-fuel mixture combustion in ICE cylinder are used after their 
expansion in cylinders to increase the pressure of a fresh charge. For 
example, the invention according to author certificate of the USSR 
#1677358, 1989 "The method of the regulation of a diesel engine having 
turbo supercharge and the diesel engine" besides usage of exhaust gases in 
a supercharge turbo compressor plant, at partial load it uses such 
measures as to shut off the group of cylinders from the fuel supply, to 
change the scheme of the air-gas path by means of valves while shutting 
out the receiver and to use the shut off group of cylinders for the 
compressing of a fresh charge delivered to the operating group of 
cylinders. 
This solution increases the efficiency of the engine when operating on 
partial regimes, but the exhaust losses reduce substantially the 
thermodynamic efficiency. 
There are some technical solutions in which the thermodynamic processes in 
ICE are optimized, for example the solution described in author 
certificate N 1806282, 1989 "The method of four-stroke internal combustion 
engine operation with disconnectable cylinders" suggest to carry out the 
fresh charge compression twice, while after the first compression the air 
is cooled thus bringing the process nearer to isothermal process, and 
after the second compression the air is heated before delivery into 
operating cylinders. 
Nevertheless, the improvement of the fresh charge compression process in 
this technical solution is carried out only for partial regimes, thus 
preventing to improve noticeably the efficiency of the fuel use, to obtain 
a principally new engine. Moreover, the air compression in the engine 
cylinder leads to increased mechanical losses. 
The technical solutions, in which the thermodynamic processes for ICE 
exhausted gas energy transmission to air being compressed are used, are 
also known. For example, the author certificate of the USSR N 1134748, 
1983 "Pressure exchanger" describes an apparatus, comprised of a drum 
having some passages with installed movable partitions which have from one 
side a connected exhaust gas collector and from the other side the 
delivery of fresh air. However, this technical solution does not allow all 
processes for fresh charge preparing and the parameters of compressed air 
which are necessary to begin combustion, thus reducing the efficiency of 
fuel energy usage. 
Among known technical solutions "The method to realize a cycle of internal 
combustion piston engine" described in author certificated of the USSR 
#17060140, 1990, is considered by the authors as a prototype. 
Taken as a prototype the method to realize a cycle of internal combustion 
piston engine consists in air compression, preparing of an air-fuel 
mixture, mixture combustion inside a cylinder with a movable piston, hot 
gas expansion and delivery of expansion work through a piston and an 
engine mechanism to an engine output shaft, while a portion of the gas 
energy is used to compress air. 
This method provides comparatively high efficiency of energy transformation 
due to a preliminary compression of a fresh charge of air and due to the 
produced hot gas usage not only in the engine cylinder but in two-stage 
expansion machine. 
However, the efficiency of a cycle in the method taken as a prototype is 
achieved due to the using of units which provide a mechanical 
transformation of energy (compressor and expansion machines) thus 
resulting in a low useful work factor and furthermore an additional 
compression of air in the engine cylinder results in losses of effective 
efficiency. 
Among known piston internal combustion engines "The power unit" described 
in author certificate of the USSR #1835460, 1990, is taken by the authors 
as a prototype for their apparatus. Taken as a prototype the piston engine 
comprises a housing with cylinders, pistons joined to a power take off 
shaft by means of a mechanism and an air-fuel mixture preparation system 
which includes a device for air compressing which uses the energy of the 
cylinder exhaust gases; this engine contains valves and a cooler of 
compressed air also. This device contains the means which improve the 
effective usage of energy of engine cylinder exhaust gases: gases are 
delivered into a turbine which drives a super charge compressor and then 
into a steam generator which produces steam used for an additional 
increase of fresh charge pressure. As a prototype apparatus additionally 
to the above mentioned mechanical transformation losses there are great 
losses in the additional loop for the free-piston compressor working 
substance, and in a steam generator during the heat transfer process. The 
complicated construction of a prototype and its dimensions do not allow 
the creation of a power unit which can win a competition with known units, 
especially for vehicles. 
The problem to be solved is maximal effective usage of the burned fuel 
energy. For this problem to be solved it is necessary: 
to increase the mean effective pressure of working gases ICE cylinders in 
several times; 
to reduce energy losses with exhaust gases and to attain gas parameters 
which are lower than critical ones thus probably allowing the elimination 
of a silencer, 
to attain a working process close to a Carnot cycle, i.e. to increase 
substantially the indicator efficiency; 
to reduce as far as possible the losses when the expansion energy of the 
working gases is transformed into the energy of compressed air. 
As a result of the solution of this problem a new technical result is 
achieved which includes the development of a principally new cycle of 
energy transformation in an internal combustion engine which achieves a 
substantially increased liter power and substantially reduced specific 
mass of an engine and its effective efficiency reaches to the value 0.85 
which is the maximal possible in thermodynamic conversions. The piston 
internal combustion engine developed to realize this cycle becomes able to 
win a competition with the best engines among known ones and its usage in 
vehicles allows access to capacious market of automobiles. 
BRIEF DESCRIPTION 
The invention is based on the developed cycle of a piston internal 
combustion engine. The cycle consists of air compression, fresh air supply 
into a combustion chamber, fuel injection into the chamber, ignition of 
the fuel-air mixture, expansion of the working gases into a thermodynamic 
energy exchanger for air compression and the release of exhaust gases. The 
compressed air is stored inside a receiver for the preparation of an 
air-fuel mixture. Fuel is mixed only with compressed air and the mixture 
is ignited at a pressure of from 14 to 770 kgf/cm.sup.2. Working gas 
expansion first takes place inside the engine cylinder up to 40% of the 
volume of the gas at atmospheric pressure, and is then carried out inside 
the thermodynamic energy exchanger where, at the expense of the remaining 
gas energy, air is compressed at a ratio of from 3 to 9 in a first stage, 
and from 3 to 24 in a second stage. Air accumulation is performed at the 
achieved parameters and the compressed air is supplied to the cylinder as 
needed by a control system command. 
The piston internal combustion engine comprises at least one cylinder with 
a piston and a thermodynamic energy exchanger linked with the engine 
cylinder and connected to a receiver through a pressure line. The receiver 
is linked to the engine cylinder through an engine inlet valve. 
According to the invention, the thermodynamic energy exchanger is designed 
as a two-stage free-piston compressor with one operating chamber connected 
to the engine cylinder through an inlet valve of the exchanger and to 
atmosphere through an outlet valve. Both valves are connected to the 
control system. The receiver is heat insulated. A valve for the supply of 
air to the engine cylinder is also connected to the control system. 
Furthermore, inlets and outlets of both air compression stages of the 
free-piston compressor are equipped with check valves. In another 
embodiment, a combustion chamber is installed between the receiver and the 
engine cylinder. 
The distinguished feature of the method of operation is that air and fuel 
are mixed and ignited at a pressure of from 14 through 770 kgf/cm.sup.2, 
the expansion of working gases first takes place inside the engine 
cylinder up to 40% of the volume of the gases at atmospheric pressure, and 
then is carried out inside the thermodynamic energy exchanger where air is 
compressed at a ratio of from 3 to 9 at the first stage, and from 3 to 24 
at the second stage, the parameters for combustion air initiated, and air 
accumulation performed at the achieved parameters. 
The two-stage air compression optimizes the process to make it close to an 
isothermal process in the first stage and to an adiabatic process in the 
second stage, thus achieving the pressure and temperature parameters for 
the compressed air which are necessary to begin fuel combustion with 
minimum energy expenditures. In this case, the most economical process is 
used to compress air since the energy exchange occurs in the thermodynamic 
exchanger where the losses are related only to losses occurred on the 
piston seal of the exchanger. Correspondingly, during expansion of the hot 
gases, a portion of the cycle work is expended inside the energy 
exchanger, and only useful work is transformed inside the engine cylinder 
into mechanical energy and transmitted to users through the engine 
mechanism 
According to the calculations of the cycle in a wide range of parameters, 
to achieve maximum useful work from the engine cylinder, hot gases should 
expand up to 40% of their volume at atmospheric pressure. The results of 
calculations for the claimed cycle in comparison with calculations for the 
engine with the same parameters (cylinder volume, suction conditions) 
working by the most efficient Otto cycle and using the same fuel (which 
defines the permissible adiabatic compression ratio) are shown in the 
following table. The octane number of the fuel which is used restricts the 
compression ratio inside the engine cylinder. As air compression according 
to the process cycle is carried out outside the cylinder, the parameters 
which could be obtained at the same adiabatic compression ratios are taken 
in order to compare this cycle with the Otto cycle. 
The table contains: isothermal compression ratio .epsilon..sub.is ; 
adiabatic compression ratio .epsilon..sub.ad ; specific volume V.sub.R at 
the point R (see FIG. 2) which is equal to V.sub.c /V.sub.ch --the 
relation of engine cylinder volume to charge volume at normal conditions; 
maximum pressure P.sub.max ; pressure in exhaust outlet P.sub.exh ; 
effective (actual) efficiency .eta..sub.e. 
TABLE 
______________________________________ 
The cycle in this invention 
V = Otto cycle 
## .epsilon..sub.is 
.epsilon..sub.ad 
V.sub.c /V.sub.ch 
P.sub.max 
P.sub.exh 
.eta..sub.e 
.epsilon..sub.ad 
P.sub.max 
P.sub.exh 
.eta..sub.e 
______________________________________ 
1 2 2 -- -- -- -- 
2 3 3 0.395 13.95 
3.58 0.325 
3 20.14 
5.10 0.149 
3 4 3 0.360 18.62 
3.42 0.375 
3 20.14 
5.10 0.149 
4 4 4 0.285 27.86 
3.05 0.440 
4 29.00 
5.12 0.184 
5 5 5 0.209 47.59 
2.65 0.512 
5 38.00 
5.08 0.210 
6 5 8 0.127 91.90 
2.23 0.582 
8 65.60 
4.88 0.258 
7 8 5 0.160 76.15 
2.30 0.560 
5 38.00 
5.08 0.210 
8 6 6 0.157 73.72 
2.35 0.559 
6 47.07 
5.01 0.229 
9 6 8 0.113 110.3 
2.11 0.597 
8 65.60 
4.88 0.258 
10 8 6 0.131 98.29 
2.15 0.584 
6 47.07 
5.01 0.229 
11 7 7 0.120 106.7 
2.12 0.593 
7 56.30 
4.95 0.245 
12 7 8 0.103 128.7 
2.01 0.608 
8 65.60 
4.88 0.258 
13 8 7 0.110 122.0 
2.03 0.602 
7 56.30 
4.95 0.245 
14 8 8 0.093 147.0 
1.93 0.617 
8 65.60 
4.88 0.258 
15 8 10 0.071 201.0 
1.78 0.639 
10 84.80 
4.77 0.278 
16 10 8 0.079 184.0 
1.79 0.630 
8 65.60 
4.88 0.258 
17 9 9 0.074 195.0 
1.78 0.636 
9 75.19 
4.82 0.268 
18 10 10 0.060 251.0 
1.65 0.650 
10 84.80 
4.77 0.278 
19 11 11 0.049 316.0 
1.54 0.661 
11 94.52 
4.72 0.286 
20 12 8 0.069 221.0 
1.68 0.639 
8 65.60 
4.88 0.258 
21 8 12 0.056 259.0 
1.67 0.655 
12 104.4 
4.67 0.293 
22 12 12 0.041 389.0 
1.45 0.670 
12 104.4 
4.67 0.293 
23 15 15 0.025 665.0 
1.24 0.689 
-- -- -- -- 
24 16 16 0.021 776.0 
1.18 0.693 
-- -- -- -- 
25 9 24 0.027 770.0 
1.20 0.700 
-- -- -- -- 
______________________________________ 
As is apparent from the table, the isobaric heat supply is not performed in 
the claimed cycle when the compression ratio is below 2*2=4 (the point R 
lies above P.sub.max), but this compression ratio is not of interest for 
piston engines. A compression ratio above 12 is not considered for an Otto 
cycle because a fuel to be used in this case is not known. There are no 
restrictions for a compression ratio in the claimed cycle and it is very 
essential when an engine operates with rarefaction in suction, for example 
as for an aviation engine. 
The volume of the engine cylinder which is used for fresh charge 
compression, fuel combustion and gas expansion is not greater than 40% of 
the volume of the engine cylinder. This substantially reduces the engine 
mass and mass related losses. In this case, only useful mechanical work is 
obtained and transmitted via the piston to a power take-off shaft. All 
energy expenditures for fresh air charge preparation are accomplished 
without using mechanisms due to thermodynamic energy converters, i.e. by 
means of most effective facilities among known ones. 
The distinguished feature of the ICE is that the thermodynamic energy 
exchanger is made as a two-stage free-piston compressor with a working 
chamber connected to the engine cylinder through an inlet valve and to the 
atmosphere through an outlet valve of the pressure exchanger. Both valves 
as wells as the valve for the air supply for the engine cylinder are 
linked to the control system. The receiver is heat insulated. Furthermore, 
inlets and outlets of both air compression stages of the free-piston 
compressor are equipped with check valves. 
The thermodynamic energy exchanger, being a free-piston compressor, 
achieves the most complete expansion of hot gases (in the case of 
sufficiently long exchanger, the expansion can be up to atmosphere 
parameters, i.e. it is possible to achieve "cold" exhaust). The cooler 
between the stages and the heat insulation of the second stage receiver 
allow the fresh charge compression process to be performed by means of a 
thermodynamically optimal method: first isothermally and then 
adiabatically. As a result, the receiver accumulates a fresh air charge, 
and this charge, according to its parameters, is ready for fuel burning by 
means of a valve both in the cylinder immediately and in an intermediate 
combustion chamber. This offers a wide variety of possibilities for engine 
power regulation and excludes unproductive losses, which reduce effective 
efficiency of known engines. Modern ICEs use only 1/3 of the fuel of an 
automobile tank to produce useful power, and the rest of the fuel is 
converted to heat losses (see Julius Mackerle "Automobils Lepsi Ucinnosti" 
Praha, 1985, SNTL-Nakladatelstvi Technike Literature, p. 13). 
Furthermore, even for the exchanger dimensions which are restricted by the 
prototype displacement (see parameter P.sub.exh in the table), a prolonged 
gas expansion in the energy exchanger obtains, at optimal compression 
ratios (.epsilon..sub.ad =9), a gas exhaust pressure, which is below 
critical (P.sub.cr =1,86), thus eliminating exhaust noise and avoiding the 
use of a silencer. Therefore, the above-mentioned distinguished features 
of the claimed invention, compared to a prototype provide substantially 
effective usage of burned fuel energy.

Referring to FIG. 1, the engine includes a housing with cylinders 1, 
pistons 2 joined by means of a crank mechanism 3 a power take off shaft 4, 
a system for air-fuel mixture preparation in which a two-stage 
thermodynamic energy exchanger 5 is used as a device for air compression, 
and a cooler 6 installed between stages of this exchanger. 
An outlet of the second stage of energy exchanger 5 is joined to 
heat-insulated receiver 7 which is connected through a valve 8 with a 
cylinder 1 of the engine. FIG. 3 shows a variant in which a combustion 
chamber 9 with a valve 10 may be installed between the receiver 7 and the 
engine cylinder 1. 
The thermodynamic energy exchanger 5 has a free piston 11 installed in a 
housing in which it creates the following cavities: a hot cavity 12 which 
is connected through a valve 13 with a cylinder 1 and through a valve 
14--with a discharge port; first stage air compression cavity 15 which is 
connected through a valve 16 with a fresh air inlet and through a valve 
17--with an inlet of the cooler 6; second stage air compression cavity 18 
which is connected through a valve 19 with an outlet of the cooler 6 and 
through a valve 20--with the receiver 7; and a damping cavity 21. Engine 
valves: 16, 17, 19, 20,--have a direct action, for example check valves of 
tag type, and valves 8, 10, 13, 14 are controlled by a control system 22. 
The cycle of the piston internal combustion engine is realized in the 
following way. 
The cycle is based on the separation of the compressing process from the 
working chamber of the ICE and its complete realization by means of the 
thermodynamic energy exchanger 5. In this situation the energy exchanger 5 
operates in a dynamic made in which a piston 11 under the action of hot 
gas pressure in the cavity 12 speeds up and then moves inertially thus 
allowing hot gases to give their energy for air compression in cavities 15 
and 18 even in conditions in which a compression resistance exceeds hot 
gas pressure. 
An operation of thermodynamic energy exchanger schematically shown in FIG. 
1 is divided into two phases. In the first phase a force of hot gas 
pressure in a cavity 12 overcomes a force created by a pressure of air 
being compressed in cavities 15 and 18. The excess force causes an 
accelerated motion of the piston 11 and piston kinetic energy increases. 
After an equalizing of forces the second phase takes place. During this 
phase kinetic energy accumulated by the piston is transformed into the 
energy of the compressed air. In this process internal energy of hot gases 
continues to transform into energy of compressed air. The energy exchange 
is completed when the piston 11 stops. The reverse exchange is prevented 
by valves 17 and 20, which close the cavities of the receiver 7 and cooler 
6. 
The kinetic energy of the piston 11 allows enough complete expansion of the 
gases in a cavity 12 until an atmospheric pressure is reached even under 
conditions when at the end of compression the pressure in the combustion 
chamber exceeds the working gas pressure. However the final pressure of 
compressed air in cavity 15 does exceed an initial pressure of the working 
gases. For further increasing of compressed air pressure it is possible to 
use two-stage compression as it is shown in FIG. 1. This scheme and two 
receivers (the volume of a cooler 6 serves as an intermediate receiver) 
give a possibility to realize air preparation for the ICE which operates 
according to working process having indicator diagram in FIG. 2. This 
diagram describes thermodynamic processes which take place in the ICE, 
thermodynamic energy exchanger and in the receivers. 
The line AF.sub.1 describes the process of isothermal compression in the 
cavity 15. When the pressure P.sub.G has been reached the air is delivered 
into a cooler 6. The line F.sub.1 G describes the delivery of all 
compressed air into the cooler 6. When the second stage air compression 
cavity 18 is being filled, air flows from cold receiver (cooler 6) and 
gives back to an exchanger 5 the work which have been made to pump air 
from low pressure cavity 15 into a cooler 6. This process is described by 
orientated segment GF.sub.2. After compression cavity 18 has been filled 
the adiabatic air compression takes place and air flows into 
heat-insulated receiver 7 (line C.sub.1 H). 
If a dead space in expansion chamber of ICE is negligible then the point H 
can be taken as the beginning of ICE operation. When a chamber volume is 
changed from 0 to V.sub.C2 air flows from receiver 7 into ICE. During this 
time ICE operates as a pneumatic motor. An isobaric heat supply occurs on 
a segment C.sub.2 Z and begins at the point C.sub.2. An adiabatic 
expansion begins at the point Z and comes to an end in initial point A for 
an ideal case. 
The distinguished feature of the indicated diagram is the introducing of a 
point R which divides the adiabatic expansion process into two fractions: 
ZR and RB. The process RB is less intensive and it takes place in the 
thermodynamic energy exchanger 5. 
Therefore, the described process is characterized by high parameters of 
working substance and by limited volume of ICE cylinder thus making this 
process closer to the working process of a steam engine. In principle, a 
diagram shown in FIG. 2 can be plotted when keeping the most important 
requirements of a Carnot cycle. The first requirement is the coincidence 
of initial and final points of the process. In order to satisfy this 
requirement the point 2 is determined by the quantity of supplied heat. 
For value V.sub.Z the adiabatic line should be plotted to pass through the 
point A and its intersection with the straight line HC.sub.2 should be 
found. Its should be noted that it is necessary to provide a proper angle 
between lines AF.sub.1 and AR for ideal coincidence of initial and final 
points. For this case the conditions for good air cooling at the first 
stage of compression should be created and all the measures should be 
taken to prevent heat removal from ICE cylinders and exchanger 5 to walls 
of the expansion chamber when working substance expansion takes place. 
The engine operates in two-stroke mode. At an initial moment of time all 
valves are closed, a piston of ICE is in top dead point (TDP) position, a 
piston of an exchanger 5 is in bottom dead point (BDP, i.e. in such 
position where a volume of a hot cavity 12 is minimal and volumes of first 
stage air compression cavity 15 and second stage air compression cavity 18 
are maximal. When ICE piston moves from TDP an inlet valve 8 begins to 
open (we consider now a case when a combustion chamber 9 and a valve 10 
are absent and fuel is injected directly to cylinder head as it is 
provided in known two-stroke ICE) and previously accumulated compressed 
air from receiver 7 flows into cylinder 1. At a proper displacement of a 
piston 2 from TDP position defined by a volume of the combustion chamber 
valve 8 is being closed and simultaneously fuel injection and fuel 
combustion take place thus producing working substance and working stroke. 
When piston 2 is in BDP outlet valve 13 is being opened and working 
substance which have transmitted partially its energy to ICE flows to 
cavity 12 of thermodynamic energy exchanger 5 in which it transmits its 
residual energy to a piston 11 and forces this piston to move to TDP 
position. In this case the air is compressed simultaneously in the first 
stage cavity 15 and in the second stage cavity 18 of the thermodynamic 
energy exchanger. When piston 11 comes to TDP position a compressed air 
from first stage air compression cavity 15 is passed through a valve 17 
into a cooler 6, and a compressed air from second stage air compression 
cavity 18 is passed through a valve 20 into receiver 7. When a piston 11 
is in TDP valves 17 and 20 are closed and then valves 14, 19, 16 are being 
opened. When a valve 19 is opened the air from cooler 6 flows under 
pressure into cavity 18 of the second stage, acts on piston 11 and moves 
it from TDP to BDP position. In this case exhaust gases from hot cavity 12 
flow through valve 14 into atmosphere and atmospheric air is sucked into 
first stage cavity 15. When piston 11 approaches BDP position valves 14 
and 16 are closed. So the air is accumulated in cavity 15 under 
atmospheric pressure and the air in cavity 18 is accumulate under pressure 
which is equal to the pressure in cooler 6. When a piston 11 travels from 
TDP to BDP due to a pressure in cavity 18 it accelerates and a 
shock-absorber is intended to brake a piston in BDP position; this 
shock-absorber may be designed as damping cavity 21 or as an additional 
energy exchanger which compresses air and delivers it to the receiver. At 
this moment a piston 2 in ICE, when moving from BDP to TDP, ejects 
residual working substance which flows out into atmosphere through an 
opened valve 13 and an opened valve 14. When a piston 2 comes to TDP 
valves 13 and 14 are closed. The cycle is repeated then. The 
serviceability of a constructive scheme shown in FIG. 1 depends on a 
relation working substance formation rate to motion velocity of piston 2. 
If a piston motion velocity exceeds a combustion rate then this scheme is 
not operable at high ICE revolution rate. In order to eliminate this 
discrepancy the combustion chamber 9 and the valve 10 are introduced 
additionally, thus extending the working substance preparation time 
without any damage to the whole process. 
Industrial applicability 
Therefore, the invention opens new possibilities to increase both 
efficiency and specific power of ICE. In essence, the new procedure is to 
organize an operation of a cycle in ICE. This procedure is based on double 
expansion of working gases in the two piston machines: in the ICE and in 
the thermodynamic energy exchanger. The expansion of gases in ICE provides 
obtaining of useful mechanical work and the expansion in the thermodynamic 
energy exchanger provides utilization of residual energy into compressed 
air energy. This procedure provides not only the energy utilization and 
reduction of specific consumption of materials for ICE due to an increase 
of mean indicator pressure in the working cylinder but simplifies the 
organization of the two-stroke operation. The new method essentially 
differs from prolonged expansion first of all in that the additional 
expansion of working gases begins not in the point where working gas 
volume is equalized with initial volume of fresh air but substantially 
earlier. If a prolonged expansion is realized in a gas turbine, then the 
work of this turbine is used to compress air preliminary which is called a 
super charge. A super charge pressure is substantially lower than a 
pressure required at the beginning of fuel combustion process. So a super 
charge needs an additional compression of air in a working cylinder. 
In the scheme being proposed the thermodynamic energy exchanger compresses 
gas until reaching a pressure sufficient to begin fuel combustion. 
According to the calculations a residual energy of exhaust gases of an 
engine, which operates in basic Otto cycle or in Diesel cycle, is not 
sufficient. A thermodynamic energy exchanger must begin its operation in 
the point R (see FIG. 2) located between points of expansion beginning and 
exhaust beginning at a basic cycle. In the point R the volume of the 
working cavity of the thermodynamic energy exchanger adds to a volume of 
the ICE and the expansion continues just in two volumes. At the end of a 
common expansion these two volumes are connected with the environment and 
the cylinder ventilation begins. This expansion of working gases is called 
separated expansion. The point R divides an expansion curve into two 
fractions. In a first fraction the mechanical work is produced, in a 
second fraction the energy of exhausted gases is transmitted to a fresh 
charge. The thermodynamic energy exchanger is a thermodynamic converter 
having a minimal mechanical losses. Modern engineering allows the use of 
known pistons having gas seals. In this case a mechanical efficiency 
should be not less than 99%. The basic mechanical losses of a claimed 
system are produced mainly during piston power stroke. 
The engine has great advantages compared with known engines in energetic 
performance, in mass and in dimensions. When having a common compression 
ratio in energy exchanger .epsilon.=100 (a first stage compression ratio 
.epsilon..sub.is =10, and a second state ratio .epsilon..sub.ad =10) the 
outlet gas temperature does not exceed 200.degree. C. (473K) and the 
volume of a net engine (and its corresponding mass) is 15 times less than 
the engine net volume. Because the engine mechanical losses are defined by 
a mass of its parts, these losses are reduced compared with known ICE 
proportionally in the same amount. 
It should be also noted that the presence of a compressed air intermediate 
cooling in the engine allows a reduction in the octane number of a fuel to 
be used. 
As it is follows from a scheme in FIG. 1, the system operated with 
two-stage air compression has 7 (or 8 in case of additional combustion 
chamber) valves. Four valves are used in a compression part of the system 
and can be made as free controllable, for example tag type valves. The 
rest of the valves should have dependent control. The main task of a 
system which controls the operation of these valves is the synchronization 
of the ICE with the thermodynamic energy exchanger. This task becomes more 
complicated because the pistons of the ICE and the thermodynamic energy 
exchanger have no mechanical coupling and can move with different 
velocities. In view of this situation the control of the valves should 
provide both the control of the ICE work and the matching of the ICE with 
the thermodynamic energy exchanger.