The present invention relates to methods and devices for using residual heat in gases which are by products of burning fossil fuels by accelerating them through convergent nozzle thus converting the internal energy stored in the gases into kinetic energy which is useful for driving turbine to generate electricity or serving as propulsion force.
Internal combustion engines use to power vehicles or stationary systems are known as low efficient energy devices since the internal friction between engine pistons and cylinders is high. This friction is pure waste of thermal energy. Further, burnt air-fuel mixture as exhaust gases are at temperature of about 300° Celsius thus contain considerable amount of energy. Today, these gases are ejected into the atmosphere without being used and as a matter of fact contribute to global warming. Overall efficiency of such engines is about 30-40%. That means the engine output useful work is only 30-40% of the total fuel burning energy.
It is desirable to make good use of heat stored in hot air used to cool engine radiators and heat stored in exhaust gases.
According to the present invention, there is provided a method and system to convert heat in exhaust gas or in hot air used to cool radiators into kinetic energy by flowing it into convergent nozzle and using this energy for generating electricity or propulsion.
A major aspect of the present invention is mixing hot gas with atmospheric air and accelerate the mixture by flowing it through convergent nozzle that accelerate the mixture of gases toward nozzle throat where the mixture is either exit as jet which provide thrust to vehicle like aircraft, land vehicle or marine vehicle or driving a turbine that drives electrical generator or provide mechanical moment for any use.
Another aspect of the invention is enclosing a combustion engine for aircraft within a flow of cooling air, and flowing this air through a convergent nozzle so that air is accelerating and ejected as high-speed jet, thus generating jet thrust that pushes the aircraft, this is a piston jet engine.
Yet another aspect of the invention is enclosing an internal combustion engine for aircraft within a flow of cooling air while the engine exhaust gases are mixed with the cooling air, and the gas mixture flows through a convergent nozzle so that the gas mixture accelerated and ejected as high-speed jet, thus generating jet thrust that pushes the aircraft, this is a piston jet engine.
Another aspect of the invention is a piston jet engine having variable exit area to adapt the exit area airspeed to various atmospheric conditions.
Yet another aspect of the invention is using internal combustion engine exhaust gases by flowing them into a stream of atmospheric air and accelerating this gas mixture by flowing it through convergent nozzle, which accelerates the mixture and the gas mixture drives a turbine which drives a electrical generator or provides its mechanical moment to any use.
Still another aspect of the invention is flowing radiator-cooling air into convergent nozzle, which accelerates the air and the accelerated air drives a turbine, which drives a electrical generator or provides its mechanical moment to any use.
Still another aspect of the invention is flowing atmospheric air and radiator-cooling air into convergent nozzle, which accelerates the air mixture that drives a turbine, which drives a electrical generator or provides its mechanical moment to any use.
Yet another aspect of the invention is flowing radiator cooling air toward a convergent nozzle while mixing it with engine exhaust gas, so that the convergent nozzle accelerates the mixture and the gas mixture drives a turbine, which drives a electrical generator or provides its mechanical moment to any use.
Yet another aspect of the invention is flowing atmospheric air and mixing it with radiator cooling air while flowing toward a convergent nozzle and mixing it with engine exhaust gas, so that the convergent nozzle accelerates the mixture and the gas mixture drives a turbine, which drives a electrical generator or provides its mechanical moment to any use.
The present invention will be further understood and appreciated from the following detailed description taken in conjunction with the drawings in which:
Note: The physics supporting this invention is compressible flow theory as presented in the Reference book: “FOUNDATIONS OF AERODYNAMICS” by A. M. KUETHE and J. D. SCHETZER Department of Aeronautical Engineering, University of Michigan—see P. I in the appendix of this application.
The present invention discloses method and devices, which put into use residual heat in gases, which are byproducts of internal combustion engines operations. A typical internal combustion engine, known also as piston engine, is very popular in driving cars, truck and small aircraft. Piston engines burn fossil fuel. The product of this burning is exhaust gas which is quite hot, about 300° Celsius, thus it contains thermal energy expressed by Enthalpy E:
E=M*C
P
*T,
Where M is the mass of the gas;
CP is the gas constant pressure specific heat;
T is the gas absolute temperature (Kelvin or Rankine scales)
Usually, this exhaust gas energy is ejected through the exhaust pipe and wasted. The heat ejected by millions of cars and trucks each day is the major contributor to global warming which put serious threat to earth normal weather and oceans' level.
While piston engine burns fuel its pistons are moving fast within their cylinders and generating friction, which heats the cylinders and the entire engine. This heat must be removed from the engine otherwise engine lubricating oil will be heated beyond its maximum allowed temperature and lose its ability to keep friction at low level. When this happens, the engine is overheated and ruined. To prevent lubricating oil from overheating, a cooling system is installed. One such system uses water that flows around the engine, warmed up and flow to a radiator where atmospheric air is forced to flow through this radiator and cools the water within the radiator so this cooled water flow back to cool the engine and so on. The “product” of this cooling system is hot air, which contains thermal energy is discarded into the atmosphere and increase global warming. Overall piston engine efficiency is about 30%, i.e. about 70% of the thermal energy produced by the burning process is more than just a waste! It is a major factor in global warming. This invention discloses an efficient method of utilizing the piston engine wasted heat by converting this wasted energy into useful energy such as electricity or mechanical power, which eventually lower the amount of burnt fuel and lower the amount of heat introduced into the atmosphere. As a byproduct, this invention also creates more economical engines.
The engine main shaft 58 drives a fan 20, which comprises of any number of blades 62 from 2 to any desirable number. Fan 20 rotates and sucks atmospheric air 30 into the pod's inlet 12. When the airflow 32,34 passes the fan, its pressure increases and it has certain velocity VI. The outer air flow 32 flows around the engine optional enclosure 50 and absorbs heat from the metal skin 50 which absorbs heat generated by the piston engine. This airflow continues to flow toward the exit 18 as airflow 34, where it mixes with airflow 58 that exit enclosure 50 through opening 57. Airflow 34 flows around the piston engine cylinders 43,47 and absorbs heat from the cylinder cooling ribs 44 then continue to flow and exit the enclosure 50 through opening 57 and optional opening 59. Optionally, burnt fuel exhaust gas 46 exits the cylinder 43 through pipe 48. It should be noted that exhaust gas 46 is very hot and while it meets airflow 32 it rapidly mix with it thus transferring its heat within the distance between opening 48 and opening 57. Therefore the temperature of airflow 34 is higher than the temperature of airflow 30. Airflow 58 temperature is also higher than airflow 30 temperature since it absorb heat from cylinders 43, 47. Finally, the airflow 35 flows into convergent nozzle 15, which according to the continuity law, forces the airflow 35 to accelerate toward the throat 18.
ρvA=constant EQ. 1—see REF book P. 155 EQ. 22—also P. 2 in the appendix of this document, accelerate airflow speed as the cross section of the nozzle 15 decreases.
The continuity law: ρvA=constant
Where: ρ is the gas density;
v is the gas speed; and
A is the flow cross section area—assuming average speed v all over this area.
Note: continuity law stems from mass conservation law. Since the gas mass rate is constant at each cross section and the speed V is increased as the cross sections decrease, that means the gas kinetic energy increases toward the throat 18 where the cross section area has a minimum. The increment of the gas kinetic energy is on the expense of the gas temperature T, according to Bernoulli's law for compressible flow:
CPT+v2/2=constant—EQ. 2—see Ref. Book P. 140 EQ 24—P. 3 in the appendix.
Where: CP is the gas constant pressure specific heat , CP]air=6000 ft-lb/slug 0R
T is gas absolute temperature (Rankine)
V is gas speed [FT/SEC]
This equation is for unit mass (in British unit system m=[slug]; in metric unit m=[KGM]. Thus, the ratio between the area cross section at 18 versus the nozzle 15 area at 59 determines the airflow 38 speed, which could be as high as Mach=1 since the fan 20 gives the airflow 32 initial speed of about 100 meter/second and in case the areas ratio is 3, that means airflow 38 has a speed of about 300 meter per second. However, the piston engine add the burnt fuel mass into the flow 30, thus the actual flow 38 speed is increased by a factor which is larger than the inlet 12 area divided by the exit area 18.
Since accelerating gas in a convergent nozzle lowers the gas temperature, according to Bernoulli's law for incompressible flow, the heat from the piston engine (exhaust flow 46 and cooling flow 58, 59) contribute significantly to the airflow 38 temperature and this increases the speed of sound (Mach=1) a at the exit according to the formula:
a=√(γRT) (a is the speed of sound);
Where: γ is CP/Cv=the ratio of Constant pressure specific heat divided by Constant volume specific heat, i.e γ=1.4 for air;
R is the gas constant (1715 ft-lb/slug 0R)
T is the absolute temperature [Rankine]
1. Calculating speed of sound for standard atmosphere at sea level where:
T=590F=5190R→a=√(γRT)=√(1.4*1715*519)=√(1,246,119)=1,116.2 FT/SEC
2. Calculating speed of sound for standard atmosphere at altitude of 10,000 FT where:
T=23.360F=483.360R→a=√(γRT)=√(1.4*1715*483.36)=√(1,160,547)=1,077.3 FT/SEC
Increasing the speed of sound at the throat 18 enables the airflow 38 getting more speed while not exceeding Mach=1, which could be a limit for low-pressure exit flow 38. Increasing the exit flow 38 speed means increasing the device thrust. Since the fan 20 efficiency is equal or more than known propeller efficiency and this device also converts the piston engine heat stored in the cooling air 58 and in the exhaust gas 46 into speed, we get more thrust from the same amount of fuel burned by the piston engine. Thus this is a jet engine powered by piston engine, which is more efficient than of a piston engine-propeller combination. Increasing the temperature of the flow 38 also increases exit flow pressure thus enable higher flow speed and consequently higher thrust.
In current piston engines for aircraft, automobiles, motor cycles and other piston engines the generated heat stored in the exhaust gas and the heat due the friction of the moving parts, especially the friction between pistons and cylinders are regarded as a problem that requires additional systems to get rid of. However in this invention, these heats are put into good use and increase engine thrust for the same amount of burnt fuel. This good use of hot gas is a major aspect of the invention.
This jet engine is more efficient than current piston engine combined with propellers since multi wing short blades 62 fan are more efficient than propellers due to increased number of blades that transfer the engine rotating power to the flow more efficiently since the fan blades are shorter than propeller blades and therefore, fans are allowed to rotate at higher RPM without reaching Mach 1 at the blades tip. Thus, fans can reach efficiency of 90% while propellers efficiency is about 80%.
A major advantage of this engine is the intake of atmospheric air 30 and accelerating it through the convergent nozzle 15 thus exploiting its natural stored heat and convert it into kinetic energy according to Bernoulli's law. Current aircraft piston engine equipped with propeller only push air rearward in order to produce thrust. In this invention air 30 is pushed rearward and further accelerated in the convergent nozzle 15, thus exploiting air natural temperature to increase engine thrust, i.e., its efficiency.
Another advantage of this invention is the mixing of hot air or gases with atmospheric air within he nozzle. This mixing of flowing gases is very rapid thus when the gas mixture arrives at the nozzle exit, it has unified temperature. It should be noted that fan may be installed in front of the pod 50 or any where in the nozzle 13 or convergent nozzle 15.
It should be noted that the exit area could be controlled by a computerized system which take into account, flight speed, flight altitude, air density or by the operator of this engine. It should be noted that fan may be installed in front of the pod 50 or any where in the nozzle 13 or convergent nozzle 15.
The optional fan 22 could be replaced by a turbine, thus exploiting the flowing air kinetic energy to generate torque to rotate the crankshaft 58. A stator 23 directs the airflow to increase the fan 22 or turbine 22 efficiency.
The same explanation of
CPT+v2/2=constant=CPT0 EQ 3—see Ref. Book P. 153 EQ 20—P. 4 in the appendix.
Where: T0 is the stagnation temperature, which is constant in isentropic compressible flow.
CP is the gas constant pressure specific heat , CP]air=6000 ft-lb/slug 0R
T is gas absolute temperature (Rankine)
V is gas speed [FT/SEC]
Thus, since the convergent nozzle 15 accelerates the flow, i.e., v in EQ (3) increases, T must decrease. (see
It should be noted that fan may be installed in front of the pod 51 or anywhere in the nozzle 13 or convergent nozzle 15.
This design could be used in hybrid cars to generate electricity from the car piston engine exhaust gas, which are currently discarded while containing precious thermal energy, which contribute to global warming. Thus this design makes good use for wasted gas produced by about 250 million cars powered by piston engines. It should be noted that the power output of turbine 150 is larger than the power required to drive fan 20 thus net power in the form of electricity is produced and can be stored by electrical battery or driving electrical motors that power car road wheels.
Another use of this device is in using hot gases generated by gas-powered turbo-generators for electricity production. In current design, the turbine burnt gases are discarded while at temperature of 200° Fahrenheit. This is a pure waste and another negative contribution to global warming. It should be noted that fan may be installed in front of the pod 12 or any where in the nozzle 13 or convergent nozzle 15.
It will be appreciated that the invention is not limited to what has been described hereinabove merely by way of example. Rather, the invention is limited solely by the claims, which follow.
Number | Date | Country | Kind |
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201610 | Oct 2009 | IL | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IL10/00852 | 10/18/2010 | WO | 00 | 4/17/2012 |