EXPERIMENTAL SETUP AND ENERGY BALANCE OF A HYBRID MICRO-COGENERATION GROUP BASED ON DIESEL ENGINE AND ORGANIC RANKINE CYCLE

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1 EXERIMENTAL SETU AND ENERGY BALANCE OF A HYBRID MICRO-COGENERATION GROU BASED ON DIESEL ENGINE AND ORGANIC RANKINE CYCLE Tudor risecaru, Alexandru Dobrovicescu, Cristian etcu, Valentin Apostol, M lina risecaru, Gheorghe opescu, Hora iu op 1, Cristina Ciobanu, Elena op, Dorin Stanciu Viorel B descu, Adrian Untea, Mahdi Hatf Kadhu Faculty of Mechanical and Mechatronics Engineering, University olitehnica of Bucharest Rokura Copany ABSTRACT The paper presents the experiental setup developed in the first stage of a Research Grant called Hybrid icro-cogeneration group of high efficiency equipped with an electronically assisted ORC (acrony GRUCOHYB). The Research Grant is in progress at the Theral Research Centre, Faculty of Mechanical and Mechatronics Engineering fro University olitehnica of Bucharest having as research partner the Rokura Copany. The hybrid icro-cogeneration group involves the use of a 40 kw Diesel engine and an Organic Rankine Cycle (ORC). A brief description of the experiental setup according to the current stage of developent has been delivered. The paper also presents the energy balance conducted in this research stage which ais to obtain the aount of waste heat available for the ORC. reliinary experiental data and results have been presented. Results show that at full load the echanical power that could be delivered by the ORC is in the range of and 7.16 kw. Future iproveent perspectives are also presented. 1. INTRODUCTION The efficiency of theral systes can be iproved by waste heat recovery. One of the ost proising solutions for waste heat recovery is the Organic Rankine Cycle (ORC) [1,2]. This technology can be successfully applied in case of electricity generators based on internal cobustion engines (ICE) by recovering heat fro exhaust and water cooling systes and converting it into work or electricity. In literature reports can be found regarding heat recovery systes based on ORC for heavy duty ICE [,4]. Results point out fuel econoy and enhanced theral efficiency. In this context, the present paper presents an experiental setup developed in the first stage of a National Research Grant called Hybrid icro-cogeneration group of high efficiency equipped with an electronically assisted ORC (acrony GRUCOHYB). The Research is in progress at the Theral Research Centre, Faculty of Mechanical and Mechatronics Engineering fro University olitehnica of Bucharest having as research partner the Rokura Copany. The hybrid icro-cogeneration group involves the use of an electricity generator based on a 40 kw overcharged Diesel engine and an ORC. At full load the electricity output is 6 kwe. The research objective is to recover heat fro the exhaust and cooling systes of the Diesel engine ant transfer it to the ORC in order to produce electricity as well as to heat a theral agent and to iprove the overall efficiency of the icro-cogeneration group. Furtherore, the paper presents the energy balance conducted for the icro-cogeneration group in order to deterine the aount of waste heat available for ORC. reliinary results are delivered based on experiental data. 1 University olitehnica of Bucharest, Faculty of Mechanical and Mechatronics Engineering, Splaiul Independen ei 1, Bucharest , Roania, , pophoratiu2001@yahoo.co. 87

2 2. EXERIMENTAL SETU DESCRITION An overview of the experiental setup according to the current stage of developent is presented in Figure Figure 1: Overview of the experiental setup The coponents visible and indexed in Figure 1 are: 1 Diesel engine; 2 electricity generator; fuel tank; 4 air flow eter; 5 exhaust pipe; 6 - air inlet pipe; 7 autoation and data acquisition panel; 8- electricity distribution syste; 9 electricity consuers. The experiental setup has any another coponents that will be presented in a uch detailed work. The instruentation available on the experiental setup and which allows conducting the energy balance is presented in Table 1. Tabelul 1: Instruentation of the experiental setup Nr. crt. Measured paraeter 1. Abient pressure [bar] 2. Abient teperature [oc]. Cobustion air volue flow rate [/h] 4. Overcharge air pressure [bar] 5. Overcharge air teperature [oc] 6. Engine intake air pressure [bar] 7. Engine intake air teperature [oc] 8. Cooling water inlet pressure [bar] 9. Cooling water inlet teperature [oc] 10. Cooling water volue flow rate [/h] 11. Cooling water outlet pressure [bar] 12. Cooling water outlet teperature [oc] 1. Turbine inlet exhaust gas pressure [bar] 88

3 14. Turbine inlet exhaust gas teperature [ o C] 15. Turbine outlet exhaust gas pressure [bar] 16. Turbine outlet exhaust gas teperature [ o C] 17. Fuel engine intake pressure [bar] 18. Exhaust gas teperature [ o C] 19. Hourly fuel consuption [l/h] 20. Active ower [kw]. ENERGY BALANCE According to the current stage of developent the energy balance equation for the experiental setup can be written as follows: fuel = + wcs + eg + rest (1) is the heat flux received through fuel cobustion; is the aount of echanical Where: fuel power produced; wcs is the heat flux rejected through the water cooling syste; eg is the heat rejected through the exhaust gases and rest is the heat flux rejected through radiation and incoplete cobustion that cannot be directly deterined in this stage. The heat flux received through fuel cobustion can be coputed as: kg / H fuel = fuel ifuel (2) Where fuel [ s] is the fuel ass flow rate and H ifuel [ kj / kg] is the inferior fuel heat value. The fuel ass flow rate can be deterined: C kg s ( 10 )/ 600] ρ [ / ] fuel = [ h fuel () In eq. (), C h [ l / h] is the hourly fuel consuption which is experientally deterined and ρ fuel [ kg / ] is the fuel density and its value is considered fro data available in literature for a teperature of 20 o C [5]. Thus ρ fuel = 822 kg /. The inferior fuel heat value is also considered fro data available in literature [5,6]: H ifuel = 42000kJ / kg. The power produced can be deterined as follows: = el ηconv [ ] (4) Where el is the aount of electric power obtained and it is directly deterined on the experiental setup; η conv is a conversion factor of echanical power into electrical power considered for the present calculation to be η conv =0.98 [7]. Next, the heat flux rejected through the water cooling syste can be coputed as follows: / kw 89

4 wcs = w cw ( te ti )[kw ] In eq. (5) w [ kg / s] is the water ass flow rate; c w [ kj /( kgk )] t e [ o C] and t i[ o C] are water teperatures at engine outlet and inlet, respectively. (5) Water ass flow rate can be deterined using experiental data as follows: V kg s ( 10 )/ 600] ρ [ / ] the water heat capacity; w = [ w w (6) Where, V w [ l / h] is the water volue flow rate easured on the experiental setup and ρ w = 1000kg / is water density. For water heat capacity the following value has been considered c w = kj /( kgk )[7]. Water teperatures at the inlet ( t i ) and outlet ( t e ) of the engine are directly easured. The heat flux ] rejected through exhaust gases is coputed as: eg [kw kw total eg = eg air [ ] (7) Where, eg total is the total heat flux available in exhaust gases and air is the heat flux due to the fresh load. The total heat flux available in exhaust gases can be deterined as: kg c T kw total eg = ge pge ge [ ] (8) In eq. (8) ge [ / s] is the exhaust gasses ass flow rate; c pge [ kj /( kgk )] is the heat capacity at constant pressure of exhaust gases and T ge [K] is the teperature of exhaust gases. Heat capacity of exhaust gases is considered fro available data in literature according to experiental data [5]. The exhaust ass flow rate is: ge = fuel + air [ kg / s] (9) The fuel ass flow rate fuel is coputed according to eq. () and the air ass flow rate air is deterined as: air = ( V air / 600) ρair[ kg / s] (11) Where, V air [ / h] is the air volue flow rate and it is experientally deterined; ρair [ kg / ] is air density coputed for abient paraeters. Thus, the heat flux due to the fresh load can be deterined: c T air = air pair air (12) 90

5 kj is the heat capacity at constant pressure and its value is c pair = kj / kgk [7] and T air is the rest is: Where, c pair /( )] considered fro data available in literature 1.01 ( ) [ kgk easured abient air teperature. Based on eqns. (1)-(12) the heat flux that cannot be directly deterined rest = fuel el wcs eg (1) As it can be noticed in eqns. (1)-(12) soe data likeh ifuel, ρ fuel and cge are adopted fro literature because in the current stage of developent the experiental setup does not allow their deterination. In future research stages Hifuel will be deterined based on fuel eleental analysis and cpge based on exhaust gases coposition derived by using a gas analyzer. 4. EXERIMENTAL RESULTS According to the energy balance described in the previous paragraph preliinary experiental investigations have been carried out for loads ranging fro 100 % to 24 %. The experiental results are presented in Table 2. Functional regie Load [%] Tabelul 2: reliinary experiental results fuel [kw] eg [kw] [kw] [kw] wcs rest [kw] air [kw] % % % % % % % The total aount of waste heat available for the ORC can be coputes as: ORC available = wcs + eg + air (14) Based on the experiental data presented in Table 2 the aount of waste heat available for ORC is presented in Table. Forer reports [,8] of waste heat recovery in case of ICE using an ORC point out theoretical efficiencies between 15 and 20%, while realistic ones are between 7 and 10%. The, aount of theoretical echanical power ORC t output [ kw ] and the realistic one output ORC provided by the ORC can be coputed as: kw, ORC t ORC t ; ORC ORC output = available ηorc output = available ηorc[ ] (15) Where, η t ORC and η ORC are theoretical and realistic efficiencies of the ORC syste respectively. If we assue for the present calculation a theoretical efficiency of ηorc t =

6 and a realistic one of ηorc = 0. 1 [], than the corresponding echanical power outputs are also presented in Table. Functional regie 5. CONCLUSIONS Tabelul : Waste heat available for ORC ORC Load [%] available [kw] ORC, t output [kw] ORC output [kw] % % % % % % % The paper presents the first stage of an original research involving a hybrid icrocogeneration group which is based on a Diesel engine and an Organic Rankine Cycle (ORC). A brief description of the experiental setup according to the current stage of developent has been done. The energy balance conducted in this research stage has been presented aiing to deterine the aount of waste heat available for the ORC. reliinary experiental results show that the ORC could deliver at 100% load a echanical power between and 7.16 kw. Future developents will include: eleental analysis of the fuel in order to obtain the inferior heat value, exhaust gas analysis which will lead to the heat capacity at constant pressure and also the aount of CO that gives the heat lost through incoplete cobustion. Also future siulation will be conducted on the heat recovery syste that will deliver data necessary for choosing the appropriate equipents for the ORC syste. References [1] Wang, H., Wang. H., Zhang Z., Optiization of Low-Teperature Exhaust Gas Waste Heat Fueled Organic Rankine Cycle, Journal of Iron and Steel Research, International, Vol. 19, Issue 6, p. 0-6, [2] Roy, J.., Ashok, M., araetric optiization and perforance analysis of a regenerative Organic Rankine Cycle using R-12 for waste heat recovery, Energy, Vol. 9, p , [] Charles, S. III, Christopher, D., Review of organic Rankine cycles for internal cobustion engine exhaust waste heat recovery, Applied Theral Engineering, Vol. 51, p , 201. [4] Ho, T.,Gerhard, R., Chris, C., AVL owertrain Engineering Inc, Waste Heavy Recovery of Heavy-Duty Diesel Engines by Organic Rankine Cycle art I: Hybrid Energy Systes of Diesel and Rankine Engines, , SAE Technical paper series, World congress, April 16-19, Detroit, [5] Kuzan, R., Tabels and Therodynaic Diagras, in roanian ublisher Editura Tehnic, Bucharest, [6] Chiriac, R., Internal cobustion engines, basic operation principles, AGIR ublishing House, Bucharest [7] Marinescu, M., Baran, N., V., Radcenco, Dobrovicescu, Al., Techinal Terodynaics, in roanian Vol. I -III, ublisher Editura Matrix Ro, Bucharest, [8] New ecological ethod for electricity generation based on heat extracted fro deep wells, in roanian, N 4 Research Grant No / , beneficiary CNM,