Claims:We claim:

1. A waste heat recovery system for naturally aspirated diesel engine (100), said system comprising:

• an air circuit to draw atmospheric and having an air filter for filtering air before being supplied to said diesel engine (100);

• an intake air heater (140) supplied with said filtered atmospheric air mixed with cold compressed air (148) received from an air compressor, said air-heater (140) preheating said air mixture by using exhaust gases tapped from an exhaust gas circuit;

• said exhaust circuit having an exhaust manifold (110) connected via an after treatment device (120) to a tail pipe (190) to release the exhaust gas to the atmosphere (200), a first portion (122) of said exhaust gas directly tapped from said exhaust manifold (120) for the recovery of the heat thereof in an EGR cooler (160), and a second portion (124) of said exhaust gas tapped after said DOC (120) for the recovery of the heat thereof in said intake air-heater (140);

• a mixing pipe (150) for mixing of said filtered and preheated air mixture with said first portion (122) of the exhaust gases cooled in said EGR cooler (160); and

• an intake manifold (180) for supplying said mixture of intake air (10) and/or cold air (148) heated with said tapped exhaust gas (122, 124);

wherein the Engine Control Unit or (ECU) of said engine controls the amount of said first portion (122) of exhaust gas to be mixed with said intake air (10) and/or cold air (148) in said mixing pipe (150) by signal (155) thereof, and/or said ECU controls the amount of said second portion (124) of the exhaust gas to be mixed with said mixture of said intake air (10) and/or cold air (148) in said air intake heater (140) to be supplied to said diesel engine via said intake manifold (180) thereof.
2. The waste heat recovery system as claimed in claim 1, wherein said after treatment device (120) is a diesel oxidation catalyst (DOC).

3. The waste heat recovery system as claimed in claim 2, wherein a first control valve (116) is provided on a pipe (118) leading from said DOC (120) to said air intake heater (140), to control the amount of said first portion (122) for mixing with said mixture of said intake air (10) and/or cold air (148) in said mixing pipe (150), by said ECU signal (155).

4. The waste heat recovery system as claimed in claim 2, wherein a second control valve (170) is provided on a pipe (162) leading from said EGR cooler (160) to said mixing pipe (150), to control the amount of said second portion (122) for mixing with said intake air (10) and/or cold air (148) in said mixing pipe (150) by said ECU signal (125).

5. The waste heat recovery system as claimed in claim 2, wherein a third control valve (134) is provided between said air filter (130) and said intake air heater (140) controlled by ECU signal (135) to control the mount of the clean filtered air (132) to be directly supplied to said mixing pipe (150) bypassing said intake air heater (140).

6. The waste heat recovery system as claimed in claim 2, wherein said intake air heater (140) comprises a tubular structure having:

• a profiled tubular heat exchange pipe (146) having an inlet (143) to receive said clean air (132) from said air filter (130) and cold air (148) from air compressor; and an outlet (144) to supply heated intake air mixture (142) to said mixing pipe (150); and

• said heat exchange pipe (146) fitted with a series of mutually parallel tubes (145) therein; an exhaust inlet pipe (118) fitted outside said heat exchange pipe (146) to supply said second portion (124) of exhaust to said mutually parallel tubes (145) for heating air coming inside said intake air heater (140); and an exhaust outlet pipe (175) for discharging said exhaust gas to a tail pipe (190) open to atmosphere;

wherein said waste heat recovery system increases the temperature of the intake air to greater than 200C or higher than the ambient temperature or the targeted air temperature.

7. The waste heat recovery system as claimed in claim 5, wherein said third control valve (134) is configured as a throttle valve to turn-off intake air bypass (136) directly supplied to said intake manifold (180) bypassing said mixing pipe (150).

8. The waste heat recovery system as claimed in claim 7, wherein said throttle valve (134) is also configured to monitor and control the flow rate of the intake air (136) supplied to said intake manifold (180) to provide maximum heat transfer at all times.

9. The waste heat recovery system as claimed in claim 8, wherein a heat sensing device (137) is disposed in the air passage between said intake air heater (140) and said intake manifold (180) measure the temperature of the intake air entering said intake manifold (180).

10. The waste heat recovery system as claimed in claim 9, wherein said throttle valve (134) is shut-off when said heat sensing device (137) signals to said ECU that the targeted intake air temperature is reached.

11. The waste heat recovery system as claimed in claim 9, wherein said throttle valve (134) is opened when said heat sensing device (137) signals to said ECU that the intake air temperature is less than said targeted temperature thereof.

Digitally Signed.

Dated: this day of 06th February 2020.

(SANJAY KESHARWANI)
APPLICANT’S PATENT AGENT
REGN. No. IN/PA-2043. , Description:FIELD OF INVENTION

The present invention relates to a waste heat recovery system in an internal combustion engine. In particular, the present invention relates to a waste heat recovery system for reducing white smoke formation in a naturally aspirated engine. More precisely, the present invention relates to a waste heat recovery system with an intake air heater using exhaust gas generated in the engine for reducing white smoke formation in a naturally aspirated engine.

BACKGROUND OF THE INVENTION

A naturally aspirated engine means an internal combustion engine, wherein the oxygen intake takes place solely at atmospheric pressure and not by a forced induction through turbocharger or supercharger.

In such naturally aspirated engines, air for combustion is sucked into cylinders of the engine by atmospheric pressure acting against a partial vacuum developed during the intake stroke when the piston travels downwards toward Bottom Dead Centre (BDC).

Due to an inherent restriction present in the engine air inlet duct including the intake manifold, with this air suction, there is a small pressure drop lowering the volumetric efficiency to < 100% and < complete air charge in the cylinder.

DISADVANTAGES OF THE PRIOR ART

The disadvantages with the conventional tractor engines, particularly in a naturally aspirated engine while operating at subzero temperatures (- 20°C to 40°C, is the production of white smoke due to the incomplete fuel combustion).
The main reasons for white smoke are:

Incorrect valve timing,

Low temperature of the fuel,

Low temperature of the intake air,

Increased Back Pressure,
Rusting of moving components, and
Wear and tear over time or because of poor maintenance.

The abovementioned problems associated with white smoke production could only be tackled with the following constraints:

Tractor’s under hood Boundary constraints,

Reducing the duration of white smoke production,

Solution to be cost-effective and simple to implement, and

Without any external energy source usage.

Therefore, there is an existing need to provide a waste heat recovery system that can use the heat of exhaust gases generated during the fuel combustion. Specifically, it is necessary to provide a waste heat recovery system including an air intake heater which can use the waste heat contained in exhaust gases released from the engine.

OBJECTS OF THE INVENTION

Some of the objects of the present invention - satisfied by at least one embodiment of the present invention - are as follows:

An object of the present invention is to provide a waste heat recovery system for naturally aspirated tractor engines.
Another object of the present invention is to provide a waste heat recovery system for naturally aspirated tractor engines, which uses waste heat content of exhaust gases produced in a tractor engine.

Still another object of the present invention is to provide a waste heat recovery system including an air intake heater for using waste heat of the exhaust gases produced in a naturally aspirated tractor engine.

A further object of the present invention is to provide an air intake heater of the waste heat recovery system, which uses the waste heat of exhaust gases produced in a naturally aspirated tractor engine.

These and other objects and advantages of the present invention will become more apparent from the following description, when read with the accompanying figures of the drawing, which are however not intended to limit the scope of the present invention in any way.

DESCRIPTION OF THE INVENTION

Heat transfer by conduction happens when there is a temperature gradient in a body (Fig.1) and energy flows from a high-temperature region to a low-temperature region. Conduction is a time-dependent mode of energy transfer. Further, the energy transfer by conduction and heat transfer per unit obtained thereby are proportional to the normal temperature gradient.

In solids, the heat transfers by convection occurs mainly by using two mechanisms, i.e.

(a) by Lattice Vibration, in which, the molecules and atoms in the high-temperature region, move faster and transfer heat to adjacent molecules due to impact, and

(b) by transportation of free electrons, in which, an energy flux occurs along the direction of decreasing temperature gradient.
In gases, the heat transfers due to the kinetic energy (KE) at the molecular level, which is a function of temperature as per the kinetic theory of gasses.

The gas molecules are in continuous random motion because of their high kinetic energy and thereby exchange energy and momentum.

Thermal Conductivity of a gas depends on the absolute temperature and is directly proportional to the square root of this absolute temperature (Fig. 2). At moderate pressure, the molecule spacing is largely compacted to the size of a molecule, thus proving the thermal conductivity to be independent of pressure.

The heat transfer occurs in liquids same as in gases. However, the atoms in liquids are more densely packed than gases and intermolecular forces also come into play.

When a molecule with high kinetic energy or at high temperature collides with a molecule with low kinetic energy and low temperature, the energy is lost or gained according to the Law of Conservation of Momentum.

The magnitude of thermal conductivity ‘k’ for a given substance depends upon the microstructure of the material and temperature at a given instant. It is a tensor property (expressing anisotropy of the property) and indicates the amount of heat flowing through per unit area when the temperature gradient is considered to be unity.

COLD CLIMATIC TESTING:

This is normally conducted in a temperature chamber for conditioning the component to subzero temperatures of about minus 40°C. These tests are done to replicate cold start conditions artificially inside a lab. The values of the flow rates and heat transfer coefficients at those temperatures can be obtained thereby.
EPA/CARB TIER-4 EMISSION NORMS IN USA:

Environment Protection Agency (EPA) in the USA signed final rule on 11th May 2004 for introducing Tier-4 emission standards, implemented in phases during 2008-2015. These standards stipulate a 90% reduction in particulate matter (PM) and Nitrogen oxides (NOx) emissions. Such stringent norms could only be obtained by using advanced exhaust gas aftertreatment technologies.

Power category Emissions NOx/NMHC/PM (g/kW h)
kW hp Tier 2 Tier 3 Tier 3 Interim Tier 4 Final
< 8 < 10 7.5/0.8 7.5/0.4
8-19 10-25 7.5/0.8 7.5/0.4
19-37 25-50 7.5/0.8 7.5/0.3 => Tier 4 Final 4.7/0.03
37-56 50-75 7.5/0.4 Option 1-> 4.7/0.3
Option 2-> 4.7/0.4 4.7/0.3
56-75 75-100 7.5/0.4 4.7/0.4 3.4/0.19/0.02 0.4/0.19/0.02
75-130 100-175 4.0/0.3 3.4/0.19/0.02 0.4/0.19/0.02
130-560 175-750 4.0/0.2 2.0/0.19/0.02 0.4/0.19/0.02
> 560 > 750 5.4/0.2 3.5/0.4/0.10 3.5/0.19/0/.02
2007 2008 2009 2010 2011 2012 2013 2014 2015 2016

DIESEL OXIDATION CATALYST (DOC):

Mainly promotes the oxidation of exhaust gas components by using oxygen amply available in diesel engine exhaust. DOC (Fig. 3) converts harmful gasses like Carbon Monoxide (CO) or Nitrogen oxides (NOx) into unharmful gases by oxidation thereof. DOC reduces the pollutants (e.g. Palladium, Platinum and aluminum oxides, being good oxidizing agents) to meet the statutory norms.
DOC operates at almost 90% efficiency. However, catalytic convertors cannot clean up particulate carbon, which causes soot content to be still present in gases available downstream DOC. Exhaust Gas Reticulation (EGR) systems are used to overcome these issues.

EXHAUST GAS RECIRCULATION (EGR):

EGR (Fig. 4) is meant for reducing NOx in Internal Combustion (IC) Engines. In EGR, a portion of the engine’s exhaust gas is returned to the engine cylinders for diluting the oxygen content of the incoming air stream and to provide gases inert to combustion to function as the absorbents of the combustion heat to reduce the peak in-cylinder temperatures. This reduces NOx emissions formed only when the fuel reacts with oxygen at very high temperatures.

Different ways in which substantial heat is lost in a conventional engine:
Ignition delay

Vibrations

Improper Coolant

Increased back pressure

Radiator blockage

Poor quality of engine oil

Rust in moving parts

Malfunctioning of the engine cooling system

Exhaust gases

The inventor/s of the present invention have brainstormed to use the actual heat losses occurring in the engine during fuel combustion to reduce this objectionable white smoke production. The most viable and promising option appeared to exploit the waste heat contained in the exhaust gases of the engine.
Therefore, an air intake heater is developed to function as a heat exchanger and to heat the intake air to a predetermined temperature before fuel combustion, by using the heat loss in the exhaust gases.

LAYOUT:

Using the present engine configuration, a boundary was determined, such that it was near the intake manifold to enable it to minimize the heat losses through the pipes and also placed as close as possible to DOC. The envelope helps to configure the pattern and develop product efficiency. The existing product is within this boundary and does not foul other engine components as well as the hood.

CALCULATIONS:

Air parameter Symbol Unit Intake air (i) Outgoing air (e)
Inlet temperature Ti/Te °C - 40 100
Outlet temperature ti/te °C 1.622869 20
Mass flow rate mo/moe kg/h 0.026073 0.026809
Specific heat cpi/cpe j/kgo 1000 506
Thermal conductivity q-i/q-e W/mK - 34.6
Density ?i/?e kg/m3 - 7115

Material parameter Unit EGR Pipe of SS
Density kg/m3 7927
Thermal conductivity W/mK 16
Specific heat j/kgo 502

Using the values given above, the length of the heat exchanger is calculated using the following formulae:

Q = UA?T
L = q/UpD?Tlm
L=q/UpD?Tlm where,
?T1-?T2
?Tlm = -----------------
ln (?T1/ ?T2)
where,
U- HTC combines
A- Area covered by the heat exchanger
L- Length of the heat exchangers

INTAKE AIR HEATER CONFIGURATION:

The intake air heater configured in accordance with the present invention, preferably has a body made with stainless steel having very little thickness so as to act as a good heat transfer medium. This intake air heat exchanger is made up of:

A pipe to carry air exhausted from DOC to heat exchanger (Fig. 7a).

This heat exchanger consists of a series of tubes (Fig. 7b sectioned view) to facilitate the heat transfer.

A hose for routing the hot inlet air to the air intake manifold.

The hose to supply cold air from the compressor to the heat exchanger.

A pipe for routing the cool exhaust gases back to the muffler/tail pipe.

The length and diameter of the tubes for heat exchange are determined by using the velocity flow rates and heat transfer coefficients of both the exhaust gas and intake air.

To reduce the length considering the given length constraint, these tubes were coiled for reducing the area of the component as well as for increasing the heat transfer area in this small length, within which the flow rates can be easily maintained. The coiled tubes are housed within a casing, through which intake air is supplied after cleaning it in the air filter. After heating the intake air, the obtained hot air is supplied to the intake manifold.
A heat-sensing device is also placed in the air passage between the heat exchanger and the intake manifold. After obtaining the desired temperature of intake air, this heat-sensing device signals the Engine Control Module (ECM) to shut down the device employing a mechanical shutdown mechanism. When ECM receives the signal of reaching the desired temperatures, a throttle installed at a link between the air filter and intake manifold, is flipped to turn off the intake air bypass. The system is restarted automatically by ECM when temperatures decrease. This throttle is also used to control and monitor the velocity flow rates of the intake air, which ensures a maximum heat transfer at all time.

ELECTRONIC CONTROL UNIT/MODULE (ECU/ECM):

ECM is a device to control one or more electrical systems or subsystems in a vehicle, e.g. tractor. ECM facilitates in controlling the mechanisms such as engine valve timings or coolant temperatures and thus improves the efficiency of the mechanical systems present therein. These systems are embedded systems that help to control and finetune designs and outputs obtained thereby.

CFD ANALYSIS – COMPUTATIONAL FLUID DYNAMICS:

CFD uses numerical analysis and algorithms to solve fluid flow situations. Gas and liquid behavior are quantified by partial differential equations representing the conservation of Mass, Momentum, and Energy.
The air heat exchanger (140) configured in accordance with the present invention was modeled for CFD simulation with ANSA mesh generation software and simulated in ANSYS-Fluent 17.2 version. The sensitivity of the simulation results with respect to the mesh and turbulence model were investigated. The CFD simulation was performed on the heat exchanger (140) with the suitable mesh and discretization scheme. By CFD modeling, the precise geometry, flow structure and temperature distribution inside the model were obtained.
BOUNDARY CONDITIONS:

Air flow rate = 93.862 kg/h

Air temperature at inlet = - 400C

Exhaust gas flow rate = 96.512 kg/h

Exhaust gas temperature at inlet = 1000C.

MATERIAL PROPERTIES:

S. No. Property/Unit Air
1 Density (kg/m3) Ideal gas
2 Specific Heat (j/kg-K) 1007 @ - 400C
1006 @ 00C
1012 @ 1000C
3 Thermal Conductivity (W/m-K) 21.03 @ - 400C
24.18 @ 00C
31.39 @ 1000C
4 Viscosity (kg/m-s) -

ASSUMPTIONS:

Ambient temperature = - 400C

Only air is used for simulation, instead of exhaust gas and air.

Air is modeled as an ideal gas.

The simulation results were used for calculating global parameters such as pressure drop. Furthermore, this data was also used for visualizing the flow and temperature fields to locate the weak areas to optimize the heat exchanger configuration by considering the recirculation and turbulent zones observed by CFD modeling.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a waste heat recovery system for naturally aspirated diesel engine, the system comprising:
an air circuit to draw atmospheric and having an air filter for filtering air before being supplied to the diesel engine;
an intake air heater supplied with the filtered atmospheric air mixed with cold compressed air received from an air compressor, the air-heater preheating the air mixture by using exhaust gases tapped from an exhaust gas circuit;
the exhaust circuit having an exhaust manifold connected via a Diesel Oxidation Catalyst to a tail pipe to release the exhaust gas to the atmosphere, a first portion of the exhaust gas directly tapped from the exhaust manifold for the recovery of the heat thereof in an EGR cooler, and a second portion of the exhaust gas tapped after the DOC for the recovery of the heat thereof in the intake air-heater;
a mixing pipe for mixing of the filtered and preheated air mixture with the first portion of the exhaust gases cooled in the EGR cooler; and
an intake manifold for supplying the mixture of intake air and/or cold air heated with the tapped exhaust gas;

wherein the Engine Control Unit/ECU of the engine controls the amount of the first portion of exhaust gas to be mixed with the intake air and/or cold air in the mixing pipe by signal thereof, and/or the ECU controls the amount of the second portion of the exhaust gas to be mixed with the mixture of the intake air and/or cold air in the air intake heater to be supplied to the diesel engine via the intake manifold thereof.

Typically, first control valve is provided on a pipe leading from the DOC to the air intake heater, to control the amount of the first portion for mixing with the mixture of the intake air and/or cold air in the mixing pipe, by the ECU signal.
Typically, a second control valve is provided on a pipe leading from the EGR cooler to the mixing pipe, to control the amount of the second portion for mixing with the intake air and/or cold air in the mixing pipe by the ECU signal.

Typically, a third control valve is provided between the air filter and the intake air heater controlled by ECU signal to control the mount of the clean filtered air to be directly supplied to the mixing pipe bypassing the intake air heater.

Typically, the intake air heater comprises a tubular structure having:

a profiled tubular heat exchange pipe having an inlet to receive the clean air from the air filter or cold air from air compressor; and an outlet to supply heated intake air mixture to the mixing pipe; and

the heat exchange pipe fitted with a series of mutually parallel tubes therein; an exhaust inlet pipe fitted outside the heat exchange pipe to supply the second portion of exhaust to the mutually parallel tubes for heating air coming inside the intake air heater; and an exhaust outlet pipe for discharging the exhaust gas to a tail pipe open to atmosphere;

wherein the waste heat recovery system increases the temperature of the intake air to greater than 200C or higher than the ambient temperature or the targeted air temperature.

Typically, the third control valve is configured as a throttle valve to turn-off intake air bypass directly supplied to the intake manifold bypassing the mixing pipe.

Typically, the throttle valve is also configured to monitor and control the flow rate of the intake air supplied to the intake manifold to provide maximum heat transfer at all times.

Typically, a heat sensing device is disposed in the air passage between the intake air heater and the intake manifold measure the temperature of the intake air entering the intake manifold.

Typically, the throttle valve is shut-off when the heat sensing device signals to the ECU that the targeted intake air temperature is reached.

Typically, the throttle valve is opened when the heat sensing device signals to the ECU that the intake air temperature is less than the targeted temperature thereof.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will be briefly described with reference to the accompanying drawings:

Figure 1 shows a graphical representation of heat flow during heat transfer by conduction process.

Figure 2 shows a graphical representation of the variation in the thermal conductivity of some of the common gases with a change in temperature.

Figure 3 shows a typical Diesel Oxidation Catalyst (DOC) used to promote oxidation of the diesel engine’s exhaust gas.

Figure 4 shows a typical Exhaust Gas Recirculation (EGR) used to reduce NOx in the internal combustion engine (ICE).

Figure 5 shows a flow diagram of the operation of a conventional heat exchanger with a mechanical flow control valve provided in a diesel engine.

Figure 6 shows a flow diagram of an electronic control unit (ECU) to control the exhaust gas flow in a diesel engine fitted with DOC and EGR.

Figure 7a shows an intake air heater for a waste heat recovery system configured in accordance with the present invention.

Figure 7b shows a partial sectional view of the intake air heater of Fig. 7a.

Figure 8 shows the computational flow dynamics (CFD) model of the intake air heater configured in accordance with the present invention.

Figure 9a shows the computational flow dynamics (CFD) contours of the static temperature (in 0C) obtained for the intake air heater configured in accordance with the present invention (as seen from above).

Figure 9b shows the computational flow dynamics (CFD) contours of the static temperature (in 0C) obtained for the intake air heater configured in accordance with the present invention (as seen from below). High-temperature is prevalent in the encircled regions (HTZ) which are directly hit by the exhaust gas.

Figure 9c shows the computational flow dynamics (CFD) contours of the static temperature (in 0C) obtained for the intake air heater (on the heat exchanger tubes seen the cross-section in Fig. 8) configured in accordance with the present invention. High-temperature is prevalent in the encircled regions (HTZ) which are directly hit by the exhaust gas.

Figure 10a shows the computational flow dynamics (CFD) contours of the static pressure (in Pa) obtained for the intake air heater configured in accordance with the present invention (as seen from above).

Figure 10b shows the computational flow dynamics (CFD) contours of the static pressure (in Pa) obtained for the intake air heater configured in accordance with the present invention (as seen from below).

Figure 10c shows the computational flow dynamics (CFD) contours of the static pressure (in Pa) obtained for the intake air heater (on the heat exchanger tubes seen the cross-section in Fig. 7b) configured in accordance with the present invention.

Figure 11a shows the computational flow dynamics (CFD) temperature (in 0C) path lines from the air-inlet of the intake air heater configured in accordance with the present invention.

Figure 11b shows the computational flow dynamics (CFD) velocity (in m/s) path lines from the exhaust-gas inlet of the intake air heater configured in accordance with the present invention.

Figure 11c shows the computational flow dynamics (CFD) the temperature (in 0C) path lines from the air-inlet and exhaust-gas inlet of the intake air heater configured in accordance with the present invention.

Figure 12 shows the measurement of temperature (in 0C) and pressure (in Pa) at various locations of the intake air heater configured by the present invention.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Figure 1 shows a graphical representation of heat flow during heat transfer by conduction process. Temperature gradient Tc indicates time-dependent energy flow by conduction. Here, heat flows from high temperature to low-temperature region of the heat exchanger body. The heat transfer/unit is proportional to the normal temperature gradient Tc.

Figure 2 shows a graphical representation of the variation in the thermal conductivity of some of the common gases with a change in temperatures thereof. Here, the relationships between the thermal conductivity and the temperatures of Hydrogen (H2), Helium (He), Methane (CH4), Air, CO2, and Argon (Ar) are shown. The specific curves depict how the thermal conductivity of these gases varies with the change in temperatures thereof.

Figure 3 shows a typical Diesel Oxidation Catalyst (DOC) as an after-treatment device, used to promote the oxidation of exhaust gas of the diesel engine by converting carbon monoxide (CO) and hydrocarbons (HC) present therein into carbon dioxide (CO2) and water (H2O). It is filled with catalytic converters like palladium, Platinum and Aluminum oxides, which are all good oxidizing agents operating at almost 90% efficiency, and thus fit to reduce pollutants present in the exhaust gases to meet mandatory requirements. However, these catalytic converters cannot clean particulate matter (PM) from diesel exhaust gases, which still contain soot in exhaust gases exiting the DOC. Exhaust Gas Recirculation (EGR) is used next to remove this soot/particulate matter.

Figure 4 shows a typical Exhaust Gas Recirculation (EGR) used to reduce NOx in the exhaust gases generated in tractor diesel engine, wherein at the top of cylinder head CH, piston P includes air inlet A1 laterally disposed and connected to inlet port C1 of the cylinder and exhaust gases E1 are expelled from the outlet port C2 thereof. A portion E2 of exhaust gases E1 is recirculated in an exhaust gas recirculation (EGR) cooler cooled by a coolant, e.g. water entering a coolant inlet W1 and exiting from a coolant outlet W2. Remaining exhaust gases E3 exit the engine. The portion of exhaust gases E2 cooled by EGR cooler are mixed with incoming air A1 before inlet port C1 of the cylinder for using some of the heat of exhaust gas tapped from the EGR cooler to heat air for combustion in the cylinder. The amount of exhaust gases E2 cooled by EGR cooler to be mixed in the incoming air A1 is controlled by ECU connected to an EGR control valve V1 connected between EGR cooler and air inlet pipe.
Figure 5 shows a flow diagram of the operation of a conventional heat exchanger with a mechanical flow control valve provided in a diesel engine. Here, atmospheric air is supplied via a mechanical flow control valve (MV1) to intake air heater. This intake air heater supplies heated air to the internal combustion engine (ICE) via an intake (IM). A bypass (BP) is also provided to directly supply atmospheric air to the intake manifold (IM) without heating. After fuel combustion in ICE, exhaust gases are produced, which contain substantial heat energy even after generating power by piston-cylinder arrangement of engine. These hot exhaust gases are supplied to diesel oxidation catalyst (DOC) functioning as an after-treatment device to convert carbon monoxide (CO) and hydrocarbons (HC) present in exhaust gases into carbon dioxide (CO2) and water (H2O). The exhaust leaving DOC still has particulate matter/ soot. These somewhat cleaner exhaust gases devoid of CO and HC may be released to the atmosphere through muffler and tail pipe (TP) without further treatment. Another mechanical flow control valve (MV2) may also be provided to redirect a part of these still hot exhaust gases to the intake air heater (AH) for heating of atmospheric air to retrieve some of the residual heat energy.

Figure 6 shows the complete set-up of a waste heat recovery system configured in accordance with the present invention to be used for a tractor diesel engine. It shows the flow diagram of an electronic control unit (ECU) controlling the exhaust gas flow in a tractor’s diesel engine fitted with both DOC and EGR. Accordingly, exhaust gases generated in the internal combustion engine (100) lead through exhaust manifold (110) and supplied via pipe (112) to diesel oxidation catalyst or DOC (120). In the air circuit, the atmospheric air (10) is drawn in and after cleaning in air filter (130), the cleaned air (132) is supplied via a pipe to intake air heater (140). The filtered airflow bypass to inlet manifold (180) is controlled by airflow throttle valve (134) actuated by engine ECU signal (135). A heat sensing device (137) is placed in the air passage between the intake heater (140) and the intake manifold (180).
Once the targeted temperature of the intake air is reached, the heat sensing device (137) signals the Engine Control Module/Unit (ECM/ECU) to shut down the intake air heater (140). The shutdown mechanism is mechanical and controlled by the ECU. A throttle valve (134) is also installed between the intake air heater (140) and the intake manifold (180). When the ECU receives signals from the heat sensing device (137) that the targeted temperature is reached, the ECU signals the throttle valve (134) to turn off the intake air bypass (136) by flipping the throttle thereof.

When the intake air temperature goes down, the waste recovery system is started by the ECU. The throttle valve (134) is also used to control and monitor the velocity flow rates of the intake air to provide the maximum heat transfer at all times. A predefined quantity of filtered air heated in intake air heater (140) may also be mixed with the compressed air (148) received from the air compressor. This heated intake air is supplied to an air mixing pipe (150). A first portion (122) of the exhaust gas is tapped from the exhaust manifold (110) and directly supplied to an exhaust gas recirculation (EGR) cooler (160) which is cooled by a coolant received via coolant inlet (W1) and which exits through a coolant outlet (W2). An EGR controller 170 is fitted between the EGR cooler (160) and the mixing pipe (150). This EGR controller (170) is also controlled by the engine ECU. A second portion (124) of exhaust gas is tapped from the pipe (114) leading to the tail pipe TP (190) releasing the exhaust gas (200) to the atmosphere.

This second portion (124) of hot exhaust gas is lead to the intake air heater or heat exchanger (140) for recovery of some of heat of the exhaust gas, which would have otherwise been wasted to the atmosphere. Finally, the heated intake air mixture (152) from the mixing pipe (150) is supplied via intake manifold (180) to the engine (100). A bypass line (136) is also provided between the intake air heater (140) and intake manifold (180) for bypassing the mixing pipe (150) and to directly supply intake air heated in the intake air heater (140) to the intake manifold (180).

Figure 7a shows an intake air heater or heat exchanger (140) for a waste heat recovery system configured in accordance with the present invention. A series of tubes (145) (see Fig. 7b) are provided inside the heat exchange pipe (146) to facilitate the heat transfer from hot exhaust gas (124) to atmospheric air (10) received via air filter (130). Another pipe (118) carries the second portion (124) of exhaust gas from DOC (120) to intake air heater or heat exchanger (140) for heating the intake air (fresh atmospheric air 132 and/or cold air 148 from the air compressor) supplied via pipe (149). The heated intake air (142) is supplied via a pipe (144) to the mixing pipe (150). Another pipe (175) is also provided for routing the substantially cooled exhaust gases back to the muffler/tail pipe (190).

Figure 7b shows a partially sectioned heat exchanger pipe (146) of the intake air heater (140) of Fig. 7a. The series of tubes (145) is provided inside the heat exchanger pipe (146) facilitate heat transfer from the second portion (124) of exhaust gas to the filtered air (132) and cold air (148) from the air compressor received in the intake air heater (140). Pipe (175) routes the cooled exhaust gas back to the muffler/tail pipe (190).

Figure 8 shows the computational flow dynamics (CFD) model of the heat exchanger pipe (146) of the intake air heater (140) configured in accordance with the present invention. It shows cold air inlet (148), hot air outlet (144), exhaust gas inlet (118), exhaust gas outlet (175) leading to tail pipe (190) and baffles (147) for fixing tubes (145) inside the heat exchanger pipe (146). This CFD model of the intake air heater (140) with the heat exchanger (146) is used to predict the temperature drop across the heat exchange pipe (146).

Figure 9a shows the computational flow dynamics (CFD) contours of the static temperature (in 0C) obtained only for the fluid temperatures inside the intake air heater (140) configured in accordance with the present invention (as seen from above).

Figure 9b shows the computational flow dynamics (CFD) contours of the static temperature (in 0C) obtained for the intake air heater (140) configured in accordance with the present invention (as seen from below).

Figure 9c shows the computational flow dynamics (CFD) contours of the static temperature (in 0C) obtained (on the heat exchanger tubes 145 seen the cross-section in Fig. 7b) for the intake air heater (140) configured in accordance with the present invention.

Figure 10a shows the computational flow dynamics (CFD) contours of the static pressure (in Pa) obtained for the intake air heater configured in accordance with the present invention (as seen from the above). The pressure at the air inlet is – 4.1 mbar, while the pressure at the exhaust inlet is – 48.92 mbar.

Figure 10b shows the computational flow dynamics (CFD) contours of the static pressure (in Pa) obtained for the intake air heater configured in accordance with the present invention (as seen from below). The pressure at air inlet is – 4.1 mbar, while pressure at exhaust inlet is – 48.92 mbar.

Figure 10c shows the computational flow dynamics (CFD) contours of the static pressure (in Pa) obtained for the intake air heater (140) configured in accordance with the present invention (on the heat exchanger tubes seen the cross-section in Fig. 7b). The pressure at air inlet is – 4.1 mbar, while pressure at the exhaust inlet is – 48.92 mbar.

Figure 11a shows the computational flow dynamics (CFD) temperature (in 0C) path lines from the air inlet of the intake air heater (140) configured in accordance with the present invention. It is evident here that the air temperature increased from the inlet to the outlet thereof.

Figure 11b shows the computational flow dynamics (CFD) velocity (in m/s) path lines from the exhaust gas inlet of the intake air heater configured in accordance with the present invention. It is evident here that the exhaust gas temperature decreased from the inlet to the outlet thereof.

Figure 11c shows the computational flow dynamics (CFD) the temperature (in 0C) path lines from the air inlet and exhaust gas inlet of the intake air heater configured in accordance with the present invention.

Figure 12 shows the measurement of temperature (in 0C) and pressure (in Pa) at various locations (1 to 8) of the intake air heater configured in accordance with the present invention. This data is tabulated below:

Location Temperature (0C) Pressure (Pa)
1 - 40 410
2 - 34 333
3 27 226
4 26 0
5 100 4892
6 94 4300
7 26 341
8 25 0

TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

The waste heat recovery (WHR) system configured in accordance with the present invention for naturally aspirated diesel engine for tractors has the following technical and economic advantages:

Facilitates an easy and simple integration of waste heat recovery system into Naturally Aspirated Tractor engine, despite little increase in the suction restriction thereby.

Exhaust flow to WHR system can be controlled both mechanically and electronically based on the hardware configuration of engines.
Intake air pre-heating helps avoiding a rise in combustion air-temperature under high or normal intake air/ambient air temperature.

Controls the pre-charge pressure by relief valves.

Exhaust gas energy used to heat the intake air temperature during starting phase of diesel engine.

Valve opening and closing depend on the atmospheric temperature.

Exhaust gases are by-passed to heat exchanger until the intake air temperature reaches a predefined temperature.

The heat exchanger efficiency is increased by features like corrugation of inner tubes periphery, no. of tubes, raw material, and lengths thereof.
Substantially higher engine efficiency during cold starting with this WHR system arrangement as compared to the conventional engine.

Substantially reduces smoke intensity w.r.t. to the operating condition by this method.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for description and not of limitation.

The description provided herein is purely by way of example and illustration. The various features and advantageous details are explained with reference to this non-limiting embodiment in the above description in accordance with the present invention.
The descriptions of well-known components and manufacturing and processing techniques are consciously omitted in this specification, so as not to unnecessarily obscure the specification.

Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

Although the embodiments presented in this disclosure have been described in terms of its preferred embodiments, a person skilled in the art may make innumerable changes, variations, modifications, alterations and/or integrations in terms of materials and method used to configure, manufacture and assemble various constituents, components, subassemblies, and assemblies, in terms of their size, shapes, orientations, and interrelationships without departing from the scope and spirit of the present invention.

The numerical values given of various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher or lower than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the disclosure unless there is a statement in the specification to the contrary.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, shall be understood to implies including a described element, integer or method step, or group of elements, integers or method steps, however, does not imply excluding any other element, integer or step, or group of elements, integers or method steps.

The use of the expression “a”, “at least” or “at least one” shall imply using one or more elements or ingredients or quantities, as used in the embodiment of the disclosure to achieve one or more of the intended objects or results of the present invention.

While considerable emphasis has been placed on the specific features of the preferred embodiment described here, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiments without departing from the principles of the invention.